Image sensors with different charge-to-voltage conversion factors and methods thereof

ABSTRACT

The image sensor includes an array of photosensitive pixels comprising at least two sets of at least one pixel, control circuit configured to generate at least two different timing signals and adapted to control an acquisition of an incident optical signal by the pixels of the array, and distribution circuit configured to respectively distribute said at least two different timing signals in said at least two sets of at least one sensor, during the same acquisition of the incident optical signal.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to French Application No. 2012379,filed on Nov. 30, 2020, which application is hereby incorporated hereinby reference.

TECHNICAL FIELD

The present invention relates generally to sensors, and, in particularembodiments, to image sensors.

BACKGROUND

Image sensors combining the visible and the infrared, usually calledRGB-IR (for the red, green and blue components of the visible “Red GreenBlue”, and an infrared component “IR”), includes a photosensitive pixelper detected component.

A “pixel” is defined as one single photosensitive site dedicated to onlyone of the detected components. Each pixel is sensitive over the entiredetected spectrum of light and is consequently provided with a filter ofthe colour of the respective component.

An “image element” is defined as a group of photosensitive pixels ofseveral components, such as a group formed by Bayer pattern of fourpixels comprising one red pixel, two green pixels and a blue pixel.

In the case of RGB-IR image sensors, a four-pixel image elementtypically comprises one red pixel, one green pixel, one blue pixel andone infrared pixel.

The pixels of the image sensors are arranged in an array comprising upto several millions of pixels or image elements. By construction, all ofthe pixels belonging to the same array are usually structurally the same(notwithstanding the respective filters of each pixel). In general, theresolution of the photosensitive sensors is expressed in number of imageelements (commercially called “pixels”, in contrast with the presentdefinitions).

Conventionally, in particular in the case of global shutteracquisitions, all the pixels of the array are controlled simultaneouslyduring an acquisition of an image.

The controls during an acquisition may conventionally comprise a phaseof resetting the pixels, an integration phase whose duration is called“time of exposure” or possibly “exposure”, and a phase of reading thecharges photogenerated during the integration.

Yet, the photosensitive pixels typically have a Quantum Efficiency “QE”in the infrared quite lower than their quantum efficiency in thevisible.

Consequently, during an acquisition adapted for the efficiency of thepixels in the visible, it is likely that the signals photogenerated bythe infrared are of poor quality, i.e. inaccurate and noisy; orconversely, during an acquisition adapted for the efficiency of thepixels in the infrared, it is likely that the signals photogenerated bythe visible spectrum are saturated.

Consequently, there is a need to improve the quality of the signalsphotogenerated by image sensors including several groups of pixelshaving different constraints, such as in particular RGB-IR type sensors.

SUMMARY

Embodiments and implementations relate to image sensors, in particularimage sensors comprising several sets of pixels, such as image sensorscombining the visible and the infrared.

According to one aspect, an image sensor includes an array ofphotosensitive pixels comprising at least two sets of at least onepixel, control circuit configured to generate at least two differenttiming signals and adapted to control an acquisition of an incidentoptical signal by the pixels of the array, and distribution circuitconfigured to respectively distribute said at least two different timingsignals in said at least two sets of at least one sensor, during thesame acquisition of the incident optical signal.

Thus, it is possible to control each set of pixels in compliance withtheir respective behaviours, or possibly according to particularconditions of the optical signal in the different sets of pixels (forexample high-luminosity areas and low-luminosity areas).

It should be recalled that a “pixel” is defined by one singlephotosensitive site dedicated to only one of the detected components,and that an “image element” is defined by a group of pixels of severalcomponents.

Consequently, one of the sets of pixels may comprise all the red, greenand blue pixels of the visible, another one of the sets of pixels maycomprise all the infrared pixels.

That being so, identical pixels having the same destination (for examplethe green pixels, or white pixels), may belong to different setscontrolled by distinct timing signals, for example according to theirpositioning in the array. Thus, some regions of the array includingidentical pixels could be controlled separately, or each image elementof the array, and possibly each pixel of the array, could respectivelyform each set and be controlled individually.

In fact, the sets may be defined by any type of segmentation of thearray of pixels, for example spatial segmentations defined according tothe position of the pixels in the array, and/or functional segmentationsdefined according to the use to which the pixels are intended.

According to one embodiment, the timing signals are adapted to control atime of exposure of the respective pixels to the incident opticalsignal.

Indeed, the time of exposure is a parameter typically allowing adjustingan acquisition for almost all possible conditions of the optical signal.

According to one embodiment, the array is arranged in rows and columnsof pixels, and the distribution circuit include a row and/or columndecoder, configured to selectively access the rows and/or the columnscorresponding to said at least two sets of at least one pixel.

In absolute terms, a row decoder allowing accessing each row separatelyand a column decoder allowing accessing each column separately enables adistribution of a unique timing signal respectively in each pixel of thearray. That being so, for practical reasons, it is not always necessaryto individually access each pixel of the array. Consequently, in anadvantageously simpler and more compact manner, the row and/or columndecoders may be configured to specifically access the sets of pixels asthey are arranged in the array.

According to one embodiment, the array comprises at least one first setof pixels configured to detect components of the visible spectrum of theincident optical signal, the control circuit are configured torespectively generate at least one first timing signal, and thedistribution circuit are configured to distribute said at least onefirst timing signal, respectively in said at least one first set ofpixels.

This may correspond to the case where one of said at least two sets isthe set of pixels of the visible spectrum, or to a case in which thepixels of the visible spectrum are divided into several first sets, thatcould thus be timed separately during the same acquisition.

And, for example, the array comprises several first sets of pixels, eachfirst set may correspond to a local region of the array.

For example, this could allow adjusting both the timing of the pixelslocated in a local region receiving a very low luminosity to avoid anunderexposure, and the timing of the pixels located in a local regionreceiving a very high luminosity to avoid an overexposure.

According to one embodiment, the array comprises at least one second setof pixels configured to detect an infrared component of the incidentoptical signal, the control circuit are configured to respectivelygenerate at least one second timing signal, and the distribution circuitare configured to distribute said at least one second timing signal,respectively in said at least one second set of pixels.

Thus, the infrared pixels may be controlled in compliance with their lowquantum efficiency in order to generate signals in useful dynamics,independently of the control of the other pixels, for example the pixelsof the visible spectrum.

According to one embodiment, the array comprises at least one third setof pixels configured to detect information on the ambient luminosity ofthe incident optical signal, such as the luminance and/or the colourtemperature and/or the scintillation, the control circuit are configuredto respectively generate at least one third timing signal, and thedistribution circuit are configured to distribute said at least onethird timing signal in respectively said at least one third set ofpixels.

In other words, in this embodiment, it is proposed to use thepossibility of control some pixels separately from the other ones,offered by the sensor according to this aspect, to incorporate in thearray of pixels, for example of the photographic type, the ambientluminosity measuring pixels, conventionally implemented in a distinctdevice (typically an Ambient Light Sensor “ALS”).

Advantageously, the third set of pixels includes a homogeneous spatiallypseudo-random distribution of isolated pixels on the surface of thearray.

Thus, only some image elements of the array “sporadically” include apixel dedicated to the measurement of the information on the ambientluminosity, instead of a pixel normally dedicated to a component of thevisible or infrared. Consequently, the information normally provided bythe pixels thus replaced in a discrete and isolated manner, could beeasily rebuilt by conventional techniques, such as techniques forextrapolating the information provided by the neighbouring pixels.

Besides, the homogeneous distribution in the surface of the arrayenables the pixels of the third set to gather information on the ambientluminosity in the entirety of the incident optical signal.

In this respect, advantageously, the image sensor further includesprocessing circuit dedicated to the third set of pixels and configuredto average and filter signals photogenerated by the pixels of the thirdset during the acquisition, so as to provide information on the overallambient luminosity of the incident optical signal.

Indeed, since it could not be considered in an array of pixels, inparticular a photographic-type one, to introduce an optical diffuser tohomogenise the entirety of the incident optical signal, this embodimentadvantageously provides for a digital processing adapted to providerelevant global information from the local points of measurements of thepixels belonging to the third set.

For example, the pixels of the third set of pixels are configured todetect multispectral components of the spectrum of the incident opticalsignal.

By “multispectral components”, it should be understood for examplecomponents that are more widely distributed over the spectrum of theincident optical signal than the RGB-IR components, including inparticular the red, green, blue primary colours, and the infrared butalso other components of the spectrum, such as ultraviolet, deeperinfrared, and non-visible colours of the visible. For example, thenumber of multispectral components of the pixels of the third set may becomprised between 5 and 25 different components.

According to another aspect, a method for capturing an image comprises ageneration of at least two different timing signals and adapted tocontrol an acquisition of an incident optical signal by pixels of anarray of photosensitive pixels comprising at least two sets of at leastone pixel, and a distribution of said at least two different timingsignals in said at least two sets of at least one pixel, during the sameacquisition of the incident optical signal.

According to one implementation, the timing comprises a control of atime of exposure of the respective pixels to the incident opticalsignal.

According to one implementation, the array is arranged in rows andcolumns of pixels, and the distribution comprising a row and/or columndecoding, to selectively access the rows and/or the columnscorresponding to said at least two sets of at least one pixel.

According to one implementation, the method comprises an acquisition ofcomponents of the visible spectrum of the incident optical signal in atleast one first set of pixels, controlled by at least one first timingsignal respectively distributed in said at least one first set ofpixels.

According to one implementation, the acquisition of the components ofthe visible spectrum of the incident optical signal is done in severalfirst sets of pixels, each corresponding to a local region of the array.

According to one implementation, the method comprises an acquisition ofan infrared component of the incident optical signal in at least onesecond set of pixels, controlled by at least one second timing signalrespectively distributed in said at least one second set of pixels.

According to one implementation, the method comprises a measurement ofinformation on the ambient luminosity of the incident optical signal,such as the luminance and/or the colour temperature and/or thescintillation, in at least one third set of pixels, controlled by atleast one third timing signal respectively distributed in said at leastone third set of pixels.

According to one implementation, the pixels of the third set of pixelsare distributed in a homogeneous spatially pseudo-random manner inisolated pixels on the surface of the array.

According to one implementation, the method further comprises aprocessing, comprising an averaging and a filtering of the signalsphotogenerated by the pixels of the third set during the acquisition, soas to provide information on the overall ambient luminosity of theincident optical signal.

According to one implementation, the measurement of the information onthe ambient luminosity of the incident optical signal comprises anacquisition of multispectral components of the spectrum of the incidentoptical signal.

According to another aspect, it is also provided an image sensorincluding an array of photosensitive pixels arranged in rows and columnsof pixels comprising at least two sets of pixels each corresponding to aregion of the array including several adjacent rows, control circuitconfigured to generate as many different timing signals as there aresets of pixels, the timing signals being adapted to control a time ofexposure of an acquisition of an incident optical signal by the pixelsof the array, and distribution circuit configured to respectivelydistribute said timing signals in said sets of pixels, during the sameacquisition of the incident optical signal.

According to one embodiment, the distribution circuit include a rowdecoder, configured to selectively access the rows of the regions of thearray corresponding to said at least two sets of pixels.

According to one embodiment, said regions of the array are located overa half-length of said adjacent rows, on either side of a median of thearray perpendicular to the direction of the rows.

According to one embodiment, the distribution circuit include a firstrow decoder dedicated to a first half of the array on one side of saidmedian, as well as a second row decoder dedicated to a second half ofthe array on other side of said median.

According to one embodiment, said regions of the array are located overthe entire length in the direction of the rows of said adjacent rows.

According to one embodiment, the control and distribution circuit areconfigured to distribute the timing signals, during said sameacquisition of the incident optical signal, so that the times ofexposure of the different sets of pixels start at the same time point,or the times of exposure of the different sets of pixels finish at thesame time point, or the times of exposure of the different sets ofpixels are distributed and included within the duration of the longesttime of exposure.

According to one embodiment, said sets of pixels comprise a first set ofpixels, a third set of pixels and, between the first set and the thirdset, a second set of pixels including at least two subsets of at leastone row of pixels, the control circuit being configured to generatefirst timing signals adapted to control a first time of exposure for thefirst set of pixels, third timing signals adapted to control a thirdtime of exposure, longer than the first time of exposure, for the thirdset of pixels, and second timing signals adapted to control second timesof exposure with durations varying monotonously between the first timeof exposure and the third time of exposure, respectively from the subsetof pixels adjacent to the first set up to the subset of pixels adjacentto the third set.

According to another aspect, it is proposed a method for capturing animage comprising a generation of at least two different timing signalsand adapted to control a time of exposure of an acquisition of anincident optical signal by pixels of an array of photosensitive pixels(RES), arranged in rows and columns of pixels, comprising as many setsof pixels as there are timing signals, each of the sets of pixelscorresponding to a physical region of the array including severaladjacent rows, the method comprising a distribution of said timingsignals respectively in said sets of pixels, during the same acquisitionof the incident optical signal.

According to one implementation, the distribution comprises a rowdecoding to selectively access the rows of the regions of the arraycorresponding to said at least two sets of pixels.

According to one implementation, the method is adapted for regions ofthe array located over a half-length of said adjacent rows, on eitherside of a median of the array perpendicular to the direction of therows.

According to one implementation, the distribution comprises a first rowdecoding dedicated to a first half of the array on one side of saidmedian, as well as a second row decoding dedicated to a second half ofthe array on the other side of said median.

According to one implementation, the method is adapted for regions ofthe array located over the entire length in the direction of the rows ofsaid adjacent rows.

According to one implementation, the generation and the distribution areadapted to distribute the timing signals, during said same acquisitionof the incident optical signal, so that the times of exposure of thedifferent sets of pixels starting at the same time point, or the timesof exposure of the different sets of pixels finishing at the same timepoint or the times of exposure of the different sets of pixels aredistributed and included within the duration of the longest time ofexposure.

According to one implementation, the generation of the timing signalscomprises a generation of first timing signals adapted to control afirst time of exposure for a first set of pixels, a generation of thirdtiming signals adapted to control a third time of exposure, longer thanthe first time of exposure for a third set of pixels, and a generationof second timing signals adapted to control second times of exposure fora second set of pixels including at least two subsets of at least onerow of pixels between the first set and the third set, the second timesof exposure having durations varying monotonously between the first timeof exposure and the third time of exposure, respectively from the subsetof pixels adjacent to the first set up to a subset of pixels adjacent tothe third set.

According to another aspect, it is proposed an image sensor as definedhereinabove, including reading circuit configured to provide readsignals resulting from an acquisition of an incident optical signal bythe pixels of the array, wherein the control circuit include a videotiming circuit configured to assess the dynamics of the image from adistribution of the amplitudes of the read signals, and to control anext acquisition of an incident optical signal with the timing signalsand a distribution of the timing signals in a frame mode if the dynamicsis lower than first threshold, in a band mode if the dynamics iscomprised between the first threshold and a second threshold, and in apixel mode if the dynamics is higher than the second threshold.

According to one embodiment, in the frame mode, the control anddistribution circuit are configured to generate timing signals adaptedto control a unique time of exposure and a distribution of these timingsignals to all pixels of the array.

According to one embodiment, in the band mode, the control anddistribution circuit are configured to generate said as many differenttiming signals as there are sets of pixels, and to distribute thesetiming signals in said sets of pixels each corresponding to a region ofthe array including several adjacent rows.

According to one embodiment, in the pixel mode, the control anddistribution circuit are configured to generate said respective timingsignals to each set of at least one pixel, and to distribute thesetiming signals in said sets of at least one respective pixel.

According to one embodiment, the video timing circuit is configured, ineach of said modes, to set the times of exposure controlled by thetiming signals of a subsequent acquisition according to the read signalsresulting from a prior acquisition, respectively in each of thedifferent sets of pixels.

According to another aspect, it is proposed a method for capturing animage as defined hereinabove, comprising:

a reading providing read signals resulting from an acquisition of anincident optical signal by the pixels of the array,

an analysis of the dynamics of the image from a distribution of theamplitudes of the read signals, and

a control of a next acquisition of an incident optical signal with thetiming signals and a distribution of the timing signals in a frame modeif the dynamics is lower than a first threshold, in a band mode if thedynamics is comprised between the first threshold and a secondthreshold, and in a pixel mode if the dynamics is higher than the secondthreshold.

According to one implementation, in the frame mode, the generation andthe distribution of the timing signals are adapted to control a uniquetime of exposure in all pixels of the array.

According to one implementation, in the band mode, the generation andthe distribution of the timing signals are adapted to control respectivetimes of exposure to each of said sets of pixels each corresponding to aregion of the array including several adjacent rows.

According to one implementation, in the pixel mode, the generation anddistribution of the timing signals are adapted to control respectivetimes of exposure to each of said sets of pixels each corresponding to aregion of the array including several adjacent rows.

According to one implementation, in each of said modes, the times ofexposure controlled by the timing signals of a subsequent acquisitionare set according to the read signals resulting from a prioracquisition, respectively in each of the different sets of pixels.

According to another aspect, it is also proposed an image sensorincluding an array of photosensitive pixels dedicated to components ofthe spectrum of the light, each pixel including a photosensitivesemiconductor region, a transfer gate coupled between the photosensitiveregion and a transfer node, the transfer node having a capacitive valuedefining a charge-to-voltage conversion factor of each pixel, whereinthe array of pixels is arranged according to a periodic pattern ofmacro-pixels each dedicated to one component, and each including atleast one first pixel and at least one second pixel dedicated to thiscomponent, the capacitive value of the transfer node of the first pixeldefining a first charge-to-voltage conversion factor, the capacitivevalue of the transfer node of the second pixel defining a secondcharge-to-voltage conversion factor different from the firstcharge-to-voltage conversion factor.

According to one embodiment, the periodic pattern of macro-pixelsincludes at least two macro-pixels dedicated to respective components,said first pixels and second pixels of said at least two macro-pixelsbeing positioned so as to be contiguous only to the first or secondpixels of another macro-pixel of the same pattern.

According to one embodiment, each macro-pixel includes two first pixelsand two second pixels, and wherein the periodic pattern of macro-pixelsincludes four macro-pixels dedicated, respectively, to four components.

According to one embodiment, the sensor includes control circuitconfigured to generate a first timing signal and a second timing signal,different and adapted to respectively control a first time of exposureand a second time of exposure of an acquisition of an incident opticalsignal by the pixels of the array and distribution circuit configured todistribute the first timing signal in said first pixels of themacro-pixels of the array, and to distribute the second timing signal insaid second pixels of the macro-pixels of the array, during the sameacquisition of the incident optical signal.

According to one embodiment, the first charge-to-voltage conversionfactor is greater than the second charge-to-voltage conversion factorand the first time of exposure is longer than the second time ofexposure.

According to another aspect, it is proposed a method for capturing animage with an image sensor as defined hereinbefore, comprising ageneration of a first timing signal and a second timing signal,different and adapted to respectively control a first time of exposureand a second time of exposure of an acquisition of an incident opticalsignal by the pixels of the array, and distribution of the first timingsignal in said first pixels of the macro-pixels of the array, and of thesecond timing signal in said second pixels of the macro-pixels of thearray, during the same acquisition of the incident optical signal.

According to one implementation, the first charge-to-voltage conversionfactor is greater than the second charge-to-voltage conversion factor,and the first time of exposure is longer than the second time ofexposure.

According to one implementation, the capture method comprises:

a reading providing first read data resulting from said same acquisitionof the incident optical signal by the first pixels of the array, andsecond read data resulting from said same acquisition of the incidentoptical signal by the second pixels of the array,a reconstruction of a high dynamic range “HDR” image, comprising anapplication of a respective normalisation gain to each read data, therespective normalisation gains being adapted to compensate for thedifference between the respective times of exposure of the pixels of thearray.

According to one implementation, the reconstruction of the HDR imagefurther comprises, before the application of the normalisation gain:

an identification, for each read data, of an exposure limit conditionamongst an overexposure condition, an underexposure condition, or anear-limit condition; and

if said read data is identified in one of said exposure limitconditions, a determination of a substitution data, replacing said readdata, from the read data resulting from an acquisition with neighbouringpixels of the array dedicated to the same component.

According to one implementation, the overexposure condition isidentified if the read data results from an acquisition with the firsttime of exposure, and if the read data has a value greater than a secondthreshold, the corresponding substitution data being determined from theread data resulting from an acquisition with the second time of exposureof said neighbouring pixels of the array.

According to one implementation, the underexposure condition isidentified if the read data results from an acquisition with the secondtime of exposure, and if the read data has a value lower than a firstthreshold, the corresponding substitution data being determined from theread data resulting from an acquisition with the first time of exposureof said neighbouring pixels of the array.

According to one implementation, the near-limit condition is identifiedif the read data has a value comprised between the first threshold andthe second threshold, the corresponding substitution data beingdetermined from the read data resulting from an acquisition with thefirst time of exposure of said neighbouring pixels of the array and fromthe read data resulting from an acquisition with the second time ofexposure of said neighbouring pixels of the array.

According to one implementation, said determination of the substitutiondata comprises a filtering calculating a weighted average value of saidread data resulting from an acquisition with neighbouring pixels of thearray, the weights being assigned to said read data according to anorientation of the spatial variations in the HDR image.

BRIEF DESCRIPTION OF THE DRAWINGS

Other advantages and features of the invention will appear uponexamining the detailed description of non-limiting embodiments andimplementations, and from the appended drawings, wherein:

FIG. 1 illustrates an example of an array of photosensitive pixels RESof a RGB-IR type image sensor;

FIG. 2 illustrates another example of an array of photosensitive pixelsRES of an RGB-type image sensor;

FIG. 3 illustrates an example of an image sensor including the array ofpixels RES described before in connection with FIG. 1 , as well ascontrol and distribution circuits;

FIG. 4 illustrates another example of the image sensor, of the same typeas that described in connection with FIG. 3 , but this time includingthe array of pixels described before in connection with FIG. 2 ;

FIG. 5 illustrates an example of an image signal digital processingmethod that could be implemented by the processor circuit;

FIG. 6A illustrates another example of the image sensor, of the sametype as that described in connection with FIGS. 3 and 4 , but this timeincluding the array of pixels comprising only pixels dedicated to thevisible spectrum of the incident optical signal;

FIG. 6B illustrates another embodiment of the example of image sensordescribed before in connection with FIG. 6A;

FIG. 6C corresponds to the embodiment described in connection with FIG.6B, wherein “transfer” bands are provided between bands having giventimes of exposure;

FIG. 7 illustrates an example of the image sensor, of the same type asthat described in connection with FIGS. 3, 4 and 6 , wherein the arrayof pixels includes both pixels dedicated to the visible spectrum, pixelsdedicated to the infrared, and pixels dedicated to the measurement ofinformation on the ambient luminosity;

FIG. 8 illustrates an embodiment of the control circuit, in particularthe video timing circuits associated to the different types of pixels

FIG. 9A illustrates an embodiment of the pixels of the array incollaboration with the implementations of image captures describedbefore in connection with FIGS. 1 to 8 ;

FIG. 9B illustrates a example of a periodic pattern of the macro-pixelsdescribed before in connection with FIG. 9A;

FIG. 10 schematically illustrates the amplitude of the first read dataand of the second read data, as a function of the luminance of theincident signal, and each according to the respective pair; and

FIG. 11 illustrates an advantageous example of obtainment of thesubstitution values described hereinbefore in connection with FIG. 10 .

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

FIG. 1 illustrates an example of an array of photosensitive pixels RESof a RGB-IR type image sensor CAPT, i.e. a photographic-type sensorcapable of capturing the image of an incident optical signal in thevisible spectrum and in the infrared spectrum.

In particular, the term “image” of an optical signal corresponds to theconvergence of the incident optical signal in a focal plane of anoptical system, such as a photographic objective, the surface of thearray RES being aligned in the focal plane.

In this respect, the array of pixels RES includes pixels R, G, Bdedicated to the components of primary colours of the visible, red,green, and blue, and pixels dedicated to the infrared IR. For brevity,the pixels will be referred to by the colours to which they arededicated.

It should be recalled that a “pixel” is defined as a one singlephotosensitive site dedicated to only one amongst the components of thespectrum, by means of a filter of the respective colour, and that an“image element” is defined as a group of photosensitive pixels ofseveral components allowing, for example, recomposing the entirespectrum detected at a given point of the optical image of the incidentoptical signal.

In the typical case of RGB-IR image sensors, a four-pixel image elementtypically comprises one red R pixel, one green V pixel, one blue B pixeland one infrared IR pixel, in a 2*2 pixel square.

That being so, the array of photosensitive pixels RES is shared indifferent sets of pixels E_L1, E_L2, E_IR which do not necessarilycorrespond to the construction of the image elements.

The segmentation of the sets of pixels E_L1, E_L2, E_IR is performed tocontrol the different sets of pixels with distinct timing signals S_L1,S_L2, S_IR, for example selected according to the position of each setin the array of pixels, and/or according to the use to which the pixelsare intended.

The timing signals S_L1, S_L2, S_IR are generated and distributed withcontrol circuit (CMD) and distribution circuit (DIST), in particular asdescried hereinafter in connection with FIG. 3 .

In particular, the timing signals S_L1, S_L2, S_IR are adapted tocontrol a time of exposure of the respective pixels during the sameacquisition of the incident optical signal.

In the example of FIG. 1 , the segmentation is defined by the functionof the pixels, and the array RES comprises two first sets E_L1, E_L2 ofpixels of the visible R, G, B and a second set E_IR comprising theinfrared IR pixels.

The segmentation is also defined spatially between the first sets E_L1,E_L2 of pixels of the visible, each corresponding to rows of blocks ofthree red R, green G, and blue B pixels (horizontally in the orientationof FIG. 1 ). The rows of either one of the first sets of pixels of thevisible E_L1, E_L2 are successively alternated in the array RES.

FIG. 2 illustrates another example of an array of photosensitive pixelsRES of an RGB-type image sensor CAPT, further comprising an ambientluminosity measuring device integrated in the array RES. The example ofFIG. 2 is not incompatible with RGB-IR type arrays, for example asdescribed in connection with FIG. 1 .

The array RES comprises a first set of pixels E_RGB including all thepixels of the visible spectrum, conventionally arranged into imageelements according to the Bayer pattern, i.e. in squares of four pixelseach including one red R pixel, two green V pixels and one blue pixel B.

The array RES further includes a third set of pixels E_ALS intended tomeasure information on the ambient luminosity of the incident opticalsignal (usually referred to as “Ambient Light Sensing”).

The adjective “third” qualifying the set of pixels intended to measurethe ambient luminosity E_ALS is given in continuation with the first setand second set, introduced before in connection with FIG. 1 . Thenumbering order of the first, second and third sets E_L1, E_L2, E_IR andE_ALS described in connection with FIGS. 1 and 2 is purely arbitrary andis intended only to nominally distinguish the different sets of pixels.

The measurement of the information on the ambient luminosity maycomprise a measurement of a luminous intensity of the incident signal, ameasurement of a chromatic temperature of the incident signal, or acharacterisation of a scintillation of a source of the incident signal.For example, the scintillation may correspond to the periods ofillumination-extinction of the LED (acronym of “Light Emitting Diode”,perfectly known to a person skilled in the art) emitters.

Consequently, the measurement of the information on the ambientluminosity does not need spatial resolution, i.e. it does not need toknow the image of the incident optical signal, and typically comprises anumber of photosensitive pixels much smaller than the number of pixelsof a photographic-type image sensor.

Indeed, the pixels of the third set of pixels E_ALS are, for example,configured to detect multispectral components of the spectrum of theincident optical signal, i.e. components distributed in the spectrum ofthe incident optical signal, such as in particular the red, green, blueprimary colours, and the infrared but also other components of thespectrum, such as ultraviolet, deeper infrared, and non-primary coloursof the visible. For example, the number of multispectral components ofthe pixels of the third set may comprise between 5 and 25 differentcomponents, and possibly up to 32 different components.

The third set E_ALS may include a few hundreds of pixels of eachcomponent, for example for a total comprised between 10,000 (tenthousand) and 50,000 (fifty thousand) pixels, which forms a number muchsmaller than the number of pixels of the visible of the array RES, forexample in the range of several millions.

Consequently, the pixels A of the third set E_ALS are disposed in anisolated manner, and according to a pseudo-random and spatiallyhomogeneous distribution in the array RES.

That being so, the density of pixels of the array RES not allowingintroducing pixels in addition to the pixels of the visible R, G, B,each pixel of the third set E_ALS takes the place of one pixel of thefirst set E_RGB.

In other words, some image elements of the array include a pixel Adedicated to the measurement of the information on the ambientluminosity, instead of a pixel normally dedicated to a component of thevisible and possibly to the infrared.

Consequently, the information normally provided by the pixels of thevisible thus sporadically replaced, i.e. in a discrete and isolatedmanner, could be easily rebuilt by conventional techniques, such astechniques for extrapolating the information provided by theneighbouring pixels.

In this respect, we will advantageously choose to replace green pixelswith the pixels of the third set E_ALS, since the green pixels aredouble in each image element of Bayer's pattern.

FIG. 3 illustrates an example of an image sensor CAPT including thearray of pixels RES described before in connection with FIG. 1 , as wellas control CMD and distribution DIST circuits.

The image sensor CAPT includes a detection circuit DET incorporating thearray of pixels RES and a control circuit CMD incorporating the controlcircuit CMD. It is considered that the distribution circuit DIST areincorporated into both the control circuit CMD and the detection circuitDET. For example, the detection circuit DET and the control circuit CMDare made integrated on respective chips.

Besides the array RES, the detection circuit DET includes power supplycircuit PWM configured to provide supply voltages to the array RES; asequencer SEQ and a row decoder DECY configured to provide sequences ofsignals controlling the operations of the array of pixels RES in amanner adapted to its architecture; and reading circuit RD configured toread the data resulting from an acquisition of an incident opticalsignal.

During an acquisition of an incident optical signal, the pixels are, forexample, controlled according to a sequence comprising a reset emptyingparasitic charges present in the photosensitive sites of the pixels; anintegration phase with a duration corresponding to the time of exposure,in which a charge amount is photogenerated by excitation of the incidentoptical signal in the photosensitive sites; a transfer phase uponcompletion of the integration phase, in which the different amounts ofphotogenerated charges are transferred towards a storage region of thepixels; and a phase of reading the charge amount stored in each storageregion of the pixels of the array RES.

The sequences of signals controlling the operations of the array ofpixels RES are derived from timing signals S_L1, S_L2, S_IR originatingfrom the control circuit CMD, usually called “video timing”, and allowin particular setting the time of exposure EXP_L1, EXP_L2, EXP_IR.

In this respect, the control circuit CMD include a video timing circuitVT_RGB dedicated to the visible, that is to say to the first sets ofpixels E_L1, E_L2, and a video timing circuit VT_IR dedicated to theinfrared, that is to say to the second set of pixels E_IR. The videotiming circuits VT_RGB, VT_IR are configured to generate the respectivetiming signals S_L1, S_L2, S_IR.

Thus, the video timing circuits VT_RGB, VT_IR of the control circuit CMDare configured to generate several different timing signals S_L1, S_L2,S_IR respectively for each set of pixels E_L1, E_L2, E_IR of the arrayRES.

The timing signals S_L1, S_L2, S_IR are adapted to control theacquisition of the incident optical signal by the pixels of the arrayRES, in particular to control the time of exposure EXP_L1, EXP_L2,EXP_IR of the pixels of each set E_L1, E_L2, E_IR.

The distribution circuit DIST, cooperating with the sequencer SEQ andthe decoder DECY, are configured to distribute the different timingsignals S_L1, S_L2, S_IR in the corresponding sets of pixels E_L1, E_L2,E_IR, during the same acquisition of the incident optical signal.

Thus, the pixels belonging to the different sets E_L1, E_L2, E_IR mayhave a time of exposure specifically established according to theirdestinations. In particular, the infrared pixels of the second set E_IRcould profit from a time of exposure longer than the red-green-bluepixels of the first sets E_L1, E_L2. For example, this allowscompensating for a charge photogeneration quantum efficiency that islower in the infrared than in the visible.

In other words, the RGB-IR image sensor is controlled to operate in anoptimum manner in each set of pixels, i.e. in this example in an optimummanner both in the visible domain via the timing signals S_L1, S_L2controlling specifically the first sets of pixels E_L1, E_L2, and in theinfrared domain via the timing signals S_IR controlling the second setof pixels E_IR.

Furthermore, the video timing circuits VT_L1, VT_L2, VT_IR may include arespective calculation circuit CTRL_RGB, CTRL_IR, for example configuredto automatically adapt the respective times of exposure EXP_L1, EXP_L2,EXP_IR according to signals continuously output from the reading circuitRD.

Moreover, the control circuit CMD includes image signal digitalprocessor circuits ISP_RGB, ISP_IR, dedicated to each set of pixels,whose functions include in particular a digital compensation for thedistinct times of exposure.

The image signal digital processor circuits ISP_RGB, ISP_IR may alsocarry out the typical image processing functions, such as spectralreconstructions of the optical signal for each image element, filtering,noise reductions, etc.

Finally, the control circuit CMD includes conventional implementationsof a power supply stage PW, of a phase-locked loop PLL type signalgenerator, and of an external communication interface, for example ofthe I²C or MIPI type (usual terminologies of technologies well known toa person skilled in the art).

FIG. 4 illustrates another example of the image sensor CAPT, of the sametype as that described in connection with FIG. 3 , but this timeincluding the array of pixels RES described before in connection withFIG. 2 .

The elements that are common with the example of image sensor CAPTdescribed in connection with FIG. 3 bear the same references and not allof them will be detailed again.

In this embodiment, the array of pixels RES includes a first set ofpixels E_RGB dedicated to the red-green-blue component of the visiblespectrum of the incident optical signal, and a third set of pixels E_ALSconfigured to measure information on the ambient luminosity of theincident optical signal.

Consequently, the control circuit CMD include the video timing circuitVT_RGB for the first set E_RGB of pixels dedicated to the visible, and avideo timing circuit VT_ALS for the third set E_ALS of the pixelsdedicated to the measurement of the ambient luminosity.

The video timing circuits VT_RGB, VT_ALS are configured to generate therespective timing signals S_RGB, S_ALS, and in particular the respectivetimes of exposure EXP_RGB, EXP_ALS.

The video timing circuit VT_ALS may also include a respectivecalculation circuit CTRL_ALS, for example to automatically adapt thetiming signals according to signals continuously output from the readingcircuit RD.

Herein again, the distribution circuit DIST cooperate with the sequencerSEQ and the decoder DECY to distribute the different timing signalsS_RGB, S_ALS in the corresponding sets of pixels E_RGB, E_ALS, duringthe same acquisition of the incident optical signal.

Nevertheless, in this embodiment, the detection circuit DET includes adecoder DEC_ALS dedicated to the pixels of the third set E_ALS, i.e. acircuit specifically intended to distribute the timing signals S_ALS inthe pixels of the third sets E_ALS.

Providing for such a dedicated decoder DEC_ALS allows accessing througha simple decoding the pixels of the third set E_ALS isolated in thearray according to a pseudo-random and spatially homogeneousdistribution.

In turn, the row decoder DECY is configured to access all the pixels ofthe array RES, except the pixels of the third set E_ALS.

It should be noted that the management of the pixels of the third setE_ALS is not incompatible with the example of RGB-IR sensor described inconnection with FIG. 3 .

The control circuit CMD includes an image signal digital processorcircuit ISP_ALS, dedicated to the third set of pixels E_ALS, andspecifically configured to obtain information on the overall incidentsignal from local measurement points. In other words, the image signaldigital processor circuit ISP_ALS is configured to digitally simulatethe effect of an optical diffuser from measurements on the image of anoptical signal focused on the plane of the array RES.

In this respect, reference is made to FIG. 5 .

FIG. 5 illustrates an example of an image signal digital processingmethod 500 that could be implemented by the processor circuit ISP_ALS.

Step 501 comprises the reception of the read signals of the pixels ofthe third set E_ALS provided by the reading circuit RD, as well as agrouping of the different multispectral components, recorded inrespective buffer memories at step 502.

Step 503 comprises an averaging and a filtering of the groups ofmeasurements of each multispectral component.

Step 504 optionally allows dividing the measured information on theambient luminosity, relative to different regions of the array RES inwhich different measurements have been performed.

Step 505 optionally allows setting an auto-exposure parameter of thepixels of the third set E_ALS.

Step 506 comprises the application of a normalisation gain to thecalculated data, according to the time of exposure EXP_ALS controlledduring the acquisition, in order to provide coherent values.

FIG. 6A illustrates another example of the image sensor CAPT, of thesame type as that described in connection with FIGS. 3 and 4 , but thistime including the array of pixels RES comprising only pixels dedicatedto the visible spectrum of the incident optical signal.

The elements that are common with the examples of image sensor CAPTdescribed in connection with FIGS. 3 and 4 bear the same references andnot all of them will be detailed again.

In this embodiment, the array RES comprises several first sets ofpixels, each corresponding to one local region R0, R1, R2, R3, . . . ,Rn of the array RES.

The video timing circuit VT_RGB is configured to generate as many timingsignals S_0, S_1, S_2, S_3, . . . , S_n as there are regions R0-Rn ofthe array, respectively distributed in each region by the distributioncircuit DIST.

In this example, the regions R0-Rn of the array RES are separatedvertically (i.e. in the columns) into two halves, one including the“even” regions R0, R2, . . . and the other one including the “odd”regions R1, R3, . . . , Rn.

In this respect, the detection circuit DET includes a sequencer SEQ_LFTand a row decoder DECY_LFT dedicated to the “even” half of the arrayRES, and a sequencer SEQ_RGT and a row decoder DECY_RGT dedicated to the“odd” half of the array RES.

Consequently, each region R0-Rn could profit from a specificallyestablished time of exposure, for example depending on whether theregions R0-Rn are more or less illuminated in comparison with apre-established use case, or automatically by an auto-exposure algorithmper region R0-Rn implemented by the calculation circuit CTRL_RGB,according to the read signals continuously provided by the readingcircuit RD.

It should be noted that the use of the local regions R0-Rn in theabove-described array RES is not incompatible with the examples of theimage sensor CAPT described in connection with FIGS. 3 and 4 .

FIG. 6B illustrates another embodiment of the example of image sensorCAPT described before in connection with FIG. 6A.

In this other example, each of the sets of pixels of the array REScorresponds to a physical region of the array RES located over a seriesof several adjacent rows. In this example, the rows in the series arecomplete, i.e. the different regions STRP0, STRP1, . . . , STRPn of thearray are located over the entire length of said adjacent rows (i.e. inthe direction of the rows, in which the rows extend), and not over thehalf-lengths of the rows respectively located on either side of a medianof the array perpendicular to the direction of the rows as described inconnection with FIG. 6A.

Thus, each of the sets of pixels STRP0-STRPn corresponds to a band ofpixels in the array RES. In the image acquired by the array RES, thebands will advantageously have a horizontal orientation, although avertical orientation could also be considered depending on theapplication of the sensor CAPT.

This suppresses the lateral distinction between the regions (on eitherside of the median), but advantageously allows for a simplification ofthe distribution circuit DIST thereby reducing the occupied surface.

Indeed, it could be advantageous to get rid of the cumulated bulk of afirst row decoder DECY_LFT and a first sequencer SEQ_LFT dedicated tothe first “even” half of the array RES, and of a second row decoderDECY_RGT and a second sequencer SEQ_RGT dedicated to the second “odd”half of the array RES, as described in connection with FIG. 6A.

Yet, in this embodiment, in an advantageously compact manner, thedistribution circuit include a row decoder DECY and a sequencer SEQ, forthe entirety of the regions of the array RES, allowing selectivelyaccessing the rows of the regions of the array corresponding to saidsets of pixels.

Moreover, in a horizontal orientation of the bands of pixels in theimage, the trigger signals S_0-S_n could advantageously be generated anddistributed by the control circuit CMD (i.e. by the video timing circuitVT_RGB) and the distribution circuit (i.e. the row decoder DECY and thesequencer SEQ) for the times of exposure EXP0-EXPn of each band tofollow an increasing and monotonous variation from the top of the imageto the bottom of the image. This means that the time of exposure EXP0 ofthe first band STRP0, the highest one in the image, is shorter than thetime of exposure EXP1 of the second band STRP1 below and adjacent to thefirst band STRP1, and so on, up to the longest time of exposure EXPn ofthe last band STRPn, the lowest one in the image.

Indeed, depending on the application of the image sensor CAPT, it ispossible to consider that the conditions of highest luminosity aretypically found in the upper portion of the image (for example: sky,sun) whereas the conditions of lowest luminosity are typically found inthe bottom portion of the image (for example: ground, shadow of aforefront object).

In particular, this distribution of the times of exposure EXP0-EXPn sisadvantageous in the context of capture of images inside a vehiclepassenger compartment, facing the passengers. Indeed, in thisacquisition type, the top portion of the image typically comprisesconditions of high luminosity (for example: panoramic windshield,sunroof, hatchback glass), the middle portion of the image typicallycomprises conditions of mean luminosity (for example: faces and bust ofthe driver), and in which the bottom portion typically comprisesconditions of low luminosity (for example: abdomen and legs of thedriver in the shadow of the dashboard).

That being so, the timing signals S_0-S_n cannot be configured so as toadapt the times of exposure according to the use cases, for exampleaccording to the type and equipment of the vehicle, and in a manner thatcould be configured by a user (for example the manufacturer of thevehicle). The case of a vehicle passenger compartment is provided asnon-limiting example.

In particular, the variation of the times of exposure EXP0-EXPn of eachband may be other than a monotonous growth from the top to the bottom ofthe image, for example so as to apply

Moreover, the image signal digital processing circuit ISP_RGB couldapply an exposure compensation gain to the read data. The exposurecompensation gains could be easily calculated according to therespective times of exposure of the sets of pixels from which said readsignals are derived, in order to compensate for the differences betweenthe times of exposure in said sets.

That being so, the time of exposure of the pixels of one region affectsthe signal-to-noise ratio of the read data, to which the human eye isvery sensitive. Thus, to avoid a degradation of the quality of the imageperceivable at the boundaries between two adjacent bands STRP/STRP1, . .. , STRPn-1/STRPn, a transition is advantageously implemented.

In this respect, reference is made to FIG. 6C.

FIG. 6C corresponds to the embodiment described in connection with FIG.6B, wherein “transfer” bands STRP1, are provided between bands STRP0,STRP2 having given times of exposure EXP0, EXP2.

For convenience, FIG. 6C corresponds to an example where the array RESincludes five sets of pixels STRP0-STRP4, i.e. the case where n=4 of theexample described in connection with FIG. 6B.

It is considered that all the pixels of the first band STRP0 arecontrolled at the same first time of exposure EXP0, all the pixels ofthe third band STRP2 are controlled at the same third time of exposureEXP2 and all the pixels of the fifth band STRP4 are controlled at thesame fifth time of exposure EXP4.

Thus, to implement the transition mechanism, the pixels of the secondband STRP1 (and of the fourth band STRP3), located between the firstband STRP0 and the third band STRP2 (resp. between the third band STRP2and the fifth band STRP4), are divided into subsets of pixels within thesecond band STRP1 (resp. the fourth band STRP3).

The subsets are analogous to the sets of pixels in that each comprisesat least one row of pixels and in that the control circuit CMD areconfigured to generate respective timing signals S_10, . . . , S1 m,(resp. S_30, . . . , S3 m) adapted to control respective times ofexposure EXP10, . . . , EXP1 m, (resp. EXP30, . . . , EXP3 m) for eachsubset of pixels of said bands STRP1 (resp. STRP3).

And, advantageously, the control circuit are configured to generate thesecond timing signals S_10, . . . , S1 m (resp. S_30, . . . , S3 m)controlling second times of exposure EXP10, . . . , EXP1 m, (resp.EXP30, . . . , EXP3 m) with durations varying monotonously between thefirst time of exposure EXP0 and the third time of exposure EXP2 (resp.between the third time of exposure EXP2 and the fifth time of exposureEXP4), applied in the subsets, respectively of the first subset ofpixels adjacent to the first set STRP0 (resp. adjacent to the third setSTRP2) up to the last subset of pixels adjacent to the third set STRP2(resp. adjacent to the fifth set STRP4).

In other words, the times of exposure of the subsets are graduallycontrolled from one subset to another subset starting from the fixedtime of exposure in the neighbouring set up to the fixed time ofexposure in the other neighbouring set, so as to uniformise thevariations, spatially in the array, of the durations of the times ofexposure.

Thus, for example, if each of the subsets of the second set STRP1comprises a row of pixels, the times of exposure EXP10-EXP1 m could beincremented by one step P1, such that P1=(EXP2-EXP0)/(m+1), where (m+1)is the number of subsets (number of rows) of the second set STRP1, andEXP1 k=EXP0-P1*(k+1). In the corresponding example for the subsets ofthe fourth set STRP3, the step P3 is expressed P3=(EXP4-EXP2)/(n+1),where (n+1) is the number of subsets (number of rows) of the fourth setSTRP3, and EXP3 k=EXP2=FP3*(k+1).

In the three embodiments described in connection with FIGS. 6A, 6B and6C, the control and distribution circuit may further advantageously beconfigured to distribute the timing signals, during said sameacquisition of the incident optical signal, so that the times ofexposure of the different sets of pixels start at the same time point,or the times of exposure of the different sets of pixels finish at thesame time point, or the times of exposure of the different sets ofpixels are distributed and included within the duration of the longesttime of exposure.

In particular, the sequencer(s) SEQ of the distribution circuit DIST maybe configured to implement the different possibilities of distributionsof the events at the beginning and at the end of exposure of therespective sets.

Advantageously, the case where the times of exposure of the differentsets of pixels start at the same time point allows for a simpleconfiguration of the distribution circuit and for a control closer totypical acquisitions.

Advantageously, the case where the times of exposure of the differentsets of pixels finish at the same time point allows profiting fromcoherent information for the readouts of the different bands of pixelsSTRP0-STRPn. Indeed, this allows in particular a “rolling readout” ofthe pixels of the array, without requiring a local intermediate storageof the read data.

Advantageously, the case where the times of exposure of the differentsets of pixels are distributed and included within the duration of thelongest time of exposure allows limiting internal “ghost effects”.“Ghost effects” are typically caused by a movement of an object of theacquired scenery between two regions whose time points of exposure aredifferent causing the presence of the same object twice in the image.

In the three embodiments described in connection with FIGS. 6A, 6B and6C, the reading circuit RD may further advantageously be configured toprovide read signals resulting from an acquisition of an incidentoptical signal by the pixels of the array, in a “continuous” manner,i.e. for example during successive acquisitions composing a videostream. Then, the control circuit may further advantageously beconfigured between a prior acquisition and a subsequent acquisition, toset the times of exposure controlled by the timing signals of thesubsequent acquisition according to the read signals resulting from theprior acquisition.

For example, this could allow having the different regions of the arrayof pixels with a respective exposure adapted in real-time to theluminosity of the portion of the scenery corresponding to this region.

Indeed, by applying an analysis of each region, the control circuitdetermine the proper exposure required for this region in order toguarantee proper read signals, i.e. neither overexposed norunderexposed, and with a good signal-to-noise ratio.

Finally, in the three embodiments described in connection with FIGS. 6A,6B and 6C, the image signal digital processor circuit ISP_RGB mayadvantageously be configured to apply to the read signals a gain adaptedto compensate for the different times of exposure, the gains beingcalculated according to the respective times of exposure of the sets ofpixels from which said read signals are derived.

Thus, the image signal digital processor circuit ISP_RGB allows aligningthe image information between the different regions STRP0-STRPm in termsof luminance and luminosity.

In this respect, the image signal digital processor circuit ISP_RGB isconfigured to receive the coordinates of the pixels related to each gainto be applied.

FIG. 7 illustrates an example of the image sensor CAPT, of the same typeas that described in connection with FIGS. 3, 4 and 6 , wherein thearray of pixels RES includes both pixels dedicated to the visiblespectrum, pixels dedicated to the infrared, and pixels dedicated to themeasurement of information on the ambient luminosity.

The elements that are common with the examples of image sensor CAPTdescribed in connection with FIGS. 3, 4 and 6 bear the same referencesand not all of them will be detailed again.

The array of pixels RES may comprise subdivisions in each set of pixels,each corresponding to a local region of the array (FIG. 6 ).

Thus, the image sensor CAPT includes:

at least one first set of pixels E_RGB configured to detect componentsof the visible spectrum of the incident optical signal, thecorresponding video timing circuit VT_RGB being configured torespectively generate at least one first timing signal S_0-S_n,respectively distributed in said at least one first set of pixels;

at least one second set of pixels E_IR configured to detect an infraredcomponent of the incident optical signal, the corresponding video timingcircuit VT_IR being configured to respectively generate at least onesecond timing signal S_0-S_n, respectively distributed in said at leastone second set of pixels;

at least one third set of pixels E_ALS configured to measure informationon the ambient luminosity of the incident optical signal, thecorresponding video timing circuit VT_ALS being configured torespectively generate at least one third timing signal S_0-S_n,respectively distributed in said at least one third set of pixels.

In this general case, the detection circuit DET includes a row detectorDECY and a column detector DECX, belonging to the distribution circuitDIST, and configured to selectively access the rows and the columns ofthe array of pixels corresponding to the different sets of pixels.

In absolute terms, one timing signal per pixel of the array RES may beprovided for in this embodiment, for example in order to control theoptimum time of exposure for the received amount of light independentlyof each pixel, forming a “HDR” (standing for “High Dynamic Range”) imagesensor CAPT.

For practical reasons, the row and/or column decoders may be configuredto specifically access the sets of pixels as these are arranged in thearray. In this respect, in the present example, the row decoder DECY mayinclude two decoders each intended for one half of the array asdescribed in connection with FIG. 6 , and each capable of distributingthe timing signals in the manner described in connection with FIGS. 1and 3 , and the column decoder may include the decoder DEC_ALS dedicatedto the third group of pixels and described in connection with FIG. 4 .

FIG. 8 illustrates an advantageous embodiment of the control circuitCMD, in particular the video timing circuits VT/CTRL associated to thedifferent types of pixels, i.e. the pixel type dedicated to the visiblecolours R, G, B, the pixel type dedicated to the infrared IR, or thepixel type dedicated to the multispectral components of the measurementof the ambient luminosity ALS.

The reading circuit RD are configured to provide read signals resultingfrom an acquisition of an incident optical signal by the pixels of thearray RES, for example during successive acquisitions of a video stream.

The readout RD provides non-normalised raw read signals 841. Startingfrom these read signals 841, an auto-exposure mechanism 810, for examplecarried out by a hardware automaton, is configured to provide, forexample in the form of histograms, the distribution of the amplitudes ofthe read signals 811.

The video timing circuit VT/CTRL is configured to assess 812 thedynamics of the image from said distribution of the amplitudes of theread signals 811. For example, the dynamics of the image may be assessedand quantified in connection with the width of the distribution of theamplitudes of the histogram 811. In this respect, statistical filtersmay possibly be implemented.

The distribution analysis circuit 812 is configured to detect 813whether the dynamics of the image Dyn is lower than a first thresholdTh1, to detect 814 whether the dynamics of the image Dyn is comprisedbetween the first threshold Th1 and a second threshold Th2, and todetect 814 whether the dynamics of the image Dyn is higher than thesecond threshold Th2.

The decision circuit 820 is configured to set the control anddistribution circuit in a frame mode if the dynamics is lower than afirst threshold 813, in a band mode 821 if the dynamics is comprisedbetween the first threshold and a second threshold 814, and in a pixelmode 822 is the dynamics is higher than the second threshold 815, forthe next acquisition of the incident optical signal.

In the frame mode, the control CMD and distribution DIST circuits areconfigured to generate timing signals adapted to control a unique timeof exposure and a distribution of these timing signals to all the pixelsof the array RES. This corresponds to a conventional control, forexample of the global shutter type, which is not necessarily of the“HDR” (“High Dynamic Range”) type.

In the band mode 821, the decision circuit 820 activates, within thecontrol CMD and distribution DIST circuits, a coordinates controller ofsets of bands of pixels 821, i.e. the bands of rows STRP0, STRP1, STRPm.Advantageously, the coordinate controller of the sets of bands of pixels821 may incorporate local auto-exposure mechanisms “AE”, i.e. dedicatedto each set of pixels STRP0, STRP1, STRPm.

The coordinate controller of the sets of bands of pixels 821 isconfigured to generate as many different timing signals S_0, S_1, . . ., S_n as there are sets of pixels, and to distribute these timingsignals in said sets of pixels STRP0, STRP1, . . . , STRPn eachcorresponding to one region of the array including several adjacentrows. For example, this corresponds to the control described before inconnection with FIGS. 6A, 6B and 6C.

In the pixel mode 822, the decision circuit 820 activates, within thecontrol CMD and distribution DIST circuits, a coordinate controller ofsets of pixels 822, i.e. the sets of at least one pixel E_L1, E_L2,E_RGB, E_ALS. Advantageously, the coordinate controller of the sets ofpixels 822 may incorporate local auto-exposure mechanisms “AE”, i.e.dedicated to each set of pixels E_L1, E_L2, E_RGB, E_ALS.

The coordinate controller of the sets of pixels 822 is configured togenerate said respective timing signals S_0, S_1, . . . , S_n, at eachset of at least one pixel, and to distribute these timing signals insaid sets of at least one respective pixel of the array RES. Forexample, this corresponds to the control described before in connectionwith FIGS. 3 to 5 .

For each of said modes, the local auto-exposure mechanisms “AE” areconfigured to adjust the times of exposure controlled by the timingsignals of a subsequent acquisition according to the read signalsresulting from a prior acquisition, respectively in each of thedifferent sets of pixels.

For example, the adjustment of the times of exposure performed by thelocal “AE” may be set by an auto-exposure algorithm 831 providing thevalues of the times of exposure 832, per set of bands of pixels or persets of at least one pixel, starting from the histograms of distributionof the amplitudes of the read signals 811.

Moreover, the coordinate controllers of the sets of pixels 821, 822 maybe configured to transmit to the image signal digital processor circuitISP_RGB the different durations of the times of exposure and thedifferent coordinates of the respective sets of pixels.

Thus, the image signal digital processor circuit ISP_RGB may apply tothe read signals the gain adapted to compensate for the different timesof exposure 842, in order to provide normalised image data 843, inparticular in terms of luminance, luminosity, and possibly in terms ofcolour temperature such as the white balance.

Moreover, the video timing circuit VT/CTRL may provide for otheroperating modes 801, such as a mode dedicated solely to the pixels ofthe ambient luminosity sensor ALS, wherein the pixels dedicated to themultispectral components are always controlled to be active whereas theother pixels of the array are deactivated.

And, besides, other parameters of the video timing circuit VT/CTRL maybe configured 802 by a “host” process, i.e. a master process adapted tocontrol and configure the image sensor.

FIG. 9A illustrates an embodiment of the pixels MPG1, MPG2, MPB, MPR ofthe array RES, particularly advantageous in collaboration with theimplementations of image captures described before in connection withFIGS. 1 to 8 .

In this example, an approach is proposed in which the array of pixelsRES is capable of performing, in a common integration, a high dynamicrange acquisition of the incident optical signal with two differentdynamics, and furthermore with a low-noise read signal, in particularfor low luminosities.

In this respect, the pixels PG11-PG14, PB1-PB4, PR1-PR4, PG21-PG22 ofthe array include a photosensitive semiconductor region PPD, a transfergate MTG coupled between the photosensitive region and a transfer nodeSN (usually called “sense node”).

In this example, the pixels of the array are advantageously in aso-called “4 T” architecture, wherein the photosensitive semiconductorregion is for example a pinched photodiode PDD, the transfer gate MTG iscontrolled by a signal TGB<n> decoded per row. That being so, thecontrol signal of the transfer gate TGB<n> may be decoded per sets ofpixels, as described before in connection with FIGS. 1 to 8 .

The transfer gate MTG allows transferring the charges photogenerated bythe photodiode PPD towards the transfer node SN, usually a floatingdiffusion node.

The transfer node SN has a capacitive value CSN1, CSN2 defining acharge-to-voltage conversion factor CVF1, CVF2 of each pixel.

The charges transferred on the transfer node SN allow controlling afirst source-follower transistor MPX, polarising a reading node CN by areading polarisation signal VD<n>.

In turn, the reading node CN has a capacitive value CCN1, and alsoallows controlling a reading source-follower transistor MSF between aread signal VRT and a reading row VX<y> decodable per columns. Aselection circuit (not represented) may be provided for on the readingnode CN, in particular in order to implement a correlateddouble-sampling reading.

Moreover, a reset transistor MRT is coupled on the transfer node SN inorder to apply a reset voltage VPIX<n> thereto adapted to rest thecharge of the transfer node SN at the beginning of integration.

In particular, the charge-to-voltage conversion factor CVF1, CVF2 ofeach pixel is inversely proportional to the capacitive value CSN1, CSN2on the transfer node and proportional to the gain of the firstsource-follower transistor MPX, i.e. “CVF˜q*SFgain/CSN”.

Thus, a decrease in the capacitive value of the transfer node CSN1, CSN2allows increasing the charge-to-voltage conversion factor CVF1, CVF2.That being so, it is desirable that the ratio between the capacitivevalue of the transfer node CSN1, CSN2 to the capacitive value of thereading node CCN1, CCN2 remains the same. Thus, the decrease in thecapacitive value of the transfer node CSN1, CSN2 may be accompanied witha decrease by the same proportion of the capacitive value of the readingnode CCN1, CCN2.

The capacitive value CSN of the transfer node SN is composed by theintrinsic capacitive value of the transfer node SN (for example, thecapacitance of the floating diffusion node), but also the parasiticcapacitive values of the architecture of the circuit, such as theintrinsic capacitive values of the transistors coupled to the transfernode SN, furthermore, a reinforcing capacitive element may possibly becoupled to the transfer node SN.

The charge-to-voltage conversion factor CVF1, CVF2 may be considered asthe gain of the sensitivity of the pixel, which reflects the smallestamount of photogenerated charge producing a voltage signal detectable bythe reading circuit, or the “threshold” or the detection “step”. Thegreater the charge-to-voltage conversion factor, the higher thesignal-to-noise factor will be (the lower the noise will be).

As a corollary, the charge-to-voltage conversion factor CVF1, CVF2 alsodefines the maximum amount of charge photogenerated at saturation(usually called “fullwell”), i.e. the amount of charge producing themaximum voltage specified on the transfer node SN or the reading nodeCN.

In the array RES, the pixels are arranged according to a periodicpattern of macro-pixels MPG1, MPB, MPR, MPG2 each including at least onefirst pixel PG11, PG14 and at least one second pixel PG12, PG13. Forexample, each macro-pixel MPG1, MPB, MPR, MPG2 includes a square of fourpixels 2×2 including two first pixels and two second pixels. Eachmacro-pixel is dedicated to one component of the detected spectrum, forexample the red, green, blue, or infrared components.

In each macro-pixel MPG1, MPB, MPR, MPG2, said at least one first pixelPG11, PG14 and said at least one second pixel PG12, PG13 are dedicatedto the same component.

The capacitive value CSN1 of the transfer node of said at least onefirst pixel PG11, PG14 defines a first charge-to-voltage conversionfactor CVF1, whereas the capacitive value CSN2 of the transfer node ofthe second node PG12, PG13 defines a second charge-to-voltage conversionfactor CVF2 different from the first charge-to-voltage conversion factorCVF1.

In this example, each of the macro-pixels (respectively MPG1; MPB; MPR,MPG2) includes two first pixels (respectively PG11, PG14, PB1, PB4, PR1,PR4, PG21, PG24) in a diagonal of the 2×2 square, and two second pixels(respectively PG12, PG13, PB2, PB3, PR2, PR3, PG22, PG23) in the otherdiagonal of the 2×2 square.

For example, it is considered that the first charge-to-voltageconversion factor CVF1 is greater than the second charge-to-voltageconversion factor CVF2.

Thus, in each macro-pixel, the first pixels have a finer sensitivity anda better signal-to-noise ratio than the second pixels, whereas thesecond pixels have a larger amount of charge at saturation “fullwell”.

Consequently, the high dynamic range HDR function is obtained, in eachmacro-pixel, in a unique integration thanks to a spatial distribution ofthe different charge-to-voltage conversion factors CVF1, CVF2 in thefirst and second pixels. In particular, this differs from conventionalhigh dynamic range HDR acquisition techniques wherein the dynamics ofthe acquisitions is distributed over time, i.e. the dynamics of thepixels of the array is modified between two distinct and typicallysuccessive over time integrations.

Consequently, the high dynamic range HDR function obtained by thespatial distribution of the charge-to-voltage conversion factors CVF1,CVF2 is adapted to a unique global shutter type acquisition.

Advantageously, the image signal digital processing ISP is configured torecover the information of a pixel of the final image from the first andsecond pixels of the blocks of 2×2 macro-pixels. In particular, and asit will be described hereinafter in connection with FIGS. 10 and 11 ,the image signal digital processing ISP may provide for a calculation ofalignment of the luminosity from a selection of the values of the firstand second pixels of each macro-pixel, and a filtering to reduceartifacts.

It should be noted that the obtainment of the low-noise high dynamicrange HDR results in reducing the resolution of the array. That beingso, some applications have considerable needs in terms of dynamic rangeand low noise, and little constraints on the resolution, someapplications impose a low resolution (limited processing and storagecapacity), and moreover, the technological advances in terms of pixelsize reduction allow compensating for the reduction of the resolution insignificantly acceptable manner on the final image.

Furthermore, it is particularly advantageous to implement the imagecapture, the control CMD and distribution DIST circuits described beforein connection with FIGS. 1 to 8 , for which the different sets of pixelscorrespond to the pixels having different charge conversion factorsCVF1, CVF2.

Indeed, the control CMD and distribution DIST circuits configured togenerate a first timing signal A controlling a first time of exposure Ain the first pixels of the macro-pixels of the array RES, and togenerate a second timing signal B controlling a second time of exposureB in the second pixels of the macro-pixels of the array RES, during thesame acquisition of an incident optical signal, allow for the readsignals derived from each macro-pixel to provide information with evenhigher high dynamic range HDR (simultaneously in one single acquisition)and with a low noise in the low luminosities.

In this context, and when the first charge-to-voltage conversion factorCVF1 is greater than the second charge-to-voltage conversion factorCVF2, the first time of exposure A is advantageously selected so as tobe longer than the second time of exposure B.

Thus, the high dynamic range HDR effects obtained by the spatialdistribution of the charge-to-voltage conversion factors and by thedistribution of the times of exposure of the same acquisition, amplifyeach other while providing a high signal-to-noise ratio.

FIG. 9B illustrates a example of a periodic pattern of the macro-pixelsMPG1, MPB, MPR, MPG2 described before in connection with FIG. 9A.

In this preferred example, the periodic pattern of macro-pixels MPG1,MPB, MPR, MPG2 includes four macro-pixels respectively dedicated to fourrespective components, for example the green component for themacro-pixel MPG1, the blue component for the macro-pixel MPB, the redcomponent for the macro-pixel MPR, and a second time the green componentfor the macro-pixel MPG2, or alternatively the infrared component forthe macro-pixel MPG.

Each macro-pixel includes two first pixels and two second pixels, i.e.the first pixels PG11, PG14 and the second pixels PG12, PG13 in themacro-pixel MPG1; the first pixels PB1, PB4 and the second pixels PB2,PB3 in the macro-pixel MPB; the first pixels PR1, PR4 and the secondpixels PR2, PR3 in the macro-pixel MPR; the first pixels PG21, PG24 andthe second pixels PG22, PG23 in the macro-pixel MPG2.

Said first pixels and second pixels of said macro-pixels of the patternare positioned so as to be contiguous only to the first or second pixelsof another macro-pixel of the same pattern.

Thus, in this example, the four macro-pixels of the pattern occupy asquare of 4×4 pixels, each macro-pixel including four pixels located atthe four corners of a square of 3×3 pixels.

In this example, the first pixels (respectively: PG11, PG14; PB1, PB4;PR1, PR4; PG21; PG24) are located in the diagonally-opposite corners ofthe 3×3 square of each macro-pixel, and the two second pixels(respectively PG12, PG13; PB2, PB3; PR2, PR3; PG22; PG23) are located inthe opposite corners in the other diagonal of the 3×3 square of eachmacro-pixel.

Thus, in the pattern of 4×4 pixels, the first pixels PG11, PG14; PB1,PB4; PR1, PR4; PG21; PG24 are grouped in two squares of 2×2 pixels indiagonal, and the second pixels PG12, PG13; PB2, PB3; PR2, PR3; PG22;PG23 are grouped together by two squares of 2×2 pixels in the otherdiagonal.

This advantageously allows simplifying the design of the distributioncircuit distributing the first and second control signals A, B, towardsthe respective first and second pixels in a grouped manner for the fourmacro-pixels.

It should be recalled that the first pixels PG11, PG14; PB1, PB4; PR1,PR4; PG21; PG24 of the pattern have a first charge-to-voltage conversionfactor CVF1, whereas the second pixels PG12, PG13; PB2, PB3; PR2, PR3;PG22; PG23 of the pattern have a second charge-to-voltage conversionfactor CVF2 different from the first charge-to-voltage conversion factorCVF1.

It should also be recalled that the first time of exposure A, longerthan the second time of exposure B, is advantageously associated to thepixels having the first charge-to-voltage conversion factor CVF1 greaterthan the second charge-to-voltage conversion factor CVF2.

In one alternative, each macro-pixel MPG1, MPB, MPR, MPG2 couldultimately provide a high dynamic range read data of the respectivecomponent PG1BIN, PBBIN, PRBIN, PG2BIN, based on the first read dataoriginating from the first pixels and on the second read dataoriginating from the second pixels, in particular upon completion of abinning processing. Nevertheless, this divides the end resolution byfour.

In a preferred alternative, the digital processing described hereinafterin connection with FIGS. 10 and 11 enables a reconstruction of a highdynamic range image, without losing resolution.

FIGS. 10 and 11 illustrate an example of implementation of a digitalprocessing of the image signals ISP, for example as mentioned before inconnection with FIGS. 3 to 8 . In particular, the digital processing ofthe image signals ISP may provide for a normalisation allowing aligningthe luminosity according to the respective times of exposure, through aselection of the values of the first and second pixels of themacro-pixels described before in connection with FIGS. 9A and 9B, and,in some cases, an interpolation comprising a weighted-average filteringto reduce artifacts perceivable by the human eye.

Consider the preferred example of the image sensor CAPT including thearray of pixels RES described before in connection with FIG. 9B.

Thus, the method for capturing an image with the image sensor CAPT,comprises a generation and a distribution of a first timing signal A andof a second timing signal B, different and adapted to control,respectively, a first time of exposure A in the first pixels PG11, PG14;PB1, PB4; PR1, PR4; PG21; PG24 of the macro-pixels of the array RES, anda second time of exposure B in the second pixels PG12, PG13; PB2, PB3;PR2, PR3; PG22; PG23 of the macro-pixels of the array RES, during thesame acquisition of an incident optical signal.

Consider that the first time of exposure A is longer than the secondtime of exposure B.

During a reading phase RD, the first pixels of the array RES generateread signals communicating first read data L(p), and the second pixelsof the array RES generate read signals communicating second read dataS(p).

The read data correspond to a measurement of the amount ofphotogenerated charges representative of the amount of incident over theduration of the acquisition, according to the position of each pixel,and also according to the time of exposure of each pixel and accordingto the sensitivity of each pixel (charge-to-voltage conversion factorCVF1, CVF2).

The image capture method advantageously comprises a digital processing,including a reconstruction of a high dynamic range “HDR” image. Thereconstruction comprises, on the one hand, an application of arespective normalisation gain to each read data Pc_in, the respectivenormalisation gains being adapted to compensate for the differencebetween the respective times of exposure of the pixels of the array.

It should be recalled that the first time of exposure A, longer than thesecond time of exposure B, is advantageously associated to the pixelshaving the first charge-to-voltage conversion factor CVF1 greater thanthe second charge-to-voltage conversion factor CVF2.

Thus, consider that the reading phase provides two types of data: thefirst read data L(p) having the first time of exposure A (longer) andwith the first pixels having the first charge-to-voltage conversionfactor CVF1 (more sensitive); and the second read data S(p) having thesecond time of exposure B (shorter) and with the first pixels having thesecond charge-to-voltage conversion factor CVF2 (less sensitive).

For concision, the pair “first time of exposure A and firstcharge-to-voltage conversion factor CVF1” will be referred to as “A-CVF1pair” or as “first time of exposure A”; and the pair “second time ofexposure B and second charge-to-voltage conversion factor CVF2” will bereferred to as “B-CVF2 pair” or as “second time of exposure B”.

Consequently, in the “normal case”, i.e. for a read data Pc_in that isneither overexpose, nor underexposed, a first gain GL(p) is provided forto compensate the first pair A-CVF1 of the first read data L(p)originating from the first pixels; whereas a second gain GS(p) allowscompensating the second pair B-CVF2 of the second read data S(p)originating from the second pixels.

The ratio expoRatio=A/B of the first time of exposure A (i.e. first pairA-CVF1) to the second time of exposure B (i.e. second pair B-CVF2) isdefined.

Two thresholds, or “inflection points”, K1 and K2, bordering theoverexposure and underexposure cases are defined.

In this respect, reference is made to FIG. 10 .

FIG. 10 schematically illustrates the amplitude DAT of the first readdata L(p) and of the second read data S(p), as a function of theluminance LUX of the incident signal, and each according to therespective pair A-CVF1, B-CVF2.

The first threshold K1, for example set at 95% of the maximum amplitude(100% DAT) of the first read data L(p) corresponds to an amplitudeK1/expoRatio of the second read data S(p), below which the second readdata S(p) are in an underexposure condition, at an equal luminance, likefor example at the point 1104.

The second threshold K2, for example set at 98% of the maximum amplitude(100% DAT) of the first read data L(p) corresponds to the amplitude ofthe first read data L(p) above which the first read data L(p) are in anoverexposure condition, like for example at the point 1103.

Thus, starting from the thresholds K1 and K2 for the first read dataL(p) and K1/expoRatio and K2/expoRatio for the second read data S(p), itis possible to identify six exposure limit conditions on the read dataPc_in (illustrated for example 1101, 1102, 1103, 1104, 1105, 1106).

And, the gain applied to each read data Pc_in is selected depending onthe condition in which said read data Pc_in is identified.

Furthermore, in so-called exposure limit conditions, comprising inparticular overexposure conditions, underexposure conditions, ornear-limit conditions, the read data Pc_in could advantageously bereplaced by a substitution data Pc_out. The substitution data Pc_out isestimated by calculation from the read data resulting from anacquisition with neighbouring pixels of the array, dedicated to the samecomponent, before the application of the normalisation gain.

A first “normal” condition, for example met at the point 1101, could beexpressed:if Pc_in=L(p) and L(p)<K1, then Pc_out=L(p)*GL(p).

This means that when the read data Pc_in results from an acquisitionwith the first time of exposure A “Pc_in=L(p)”, and if the read dataPc_in has a value lower than the first threshold K1 “L(p)<K1”, then thegain applied to the read data Pc_in is the first gain GL(p).

A second “normal” condition, for example met at the point 1106, could beexpressed:if Pc_in=S(p) and S(p)>K2/expoRatio, then Pc_out=S(p)*GS(p).

This means that when the read data Pc_in results from an acquisitionwith the second time of exposure B “Pc_in=S(p)”, and if the read dataPc_in has a value higher than the second threshold K2/expoRatio“S(p)>K2/expoRatio 1”, then the gain applied to the read data Pc_in isthe second gain SL(p).

The overexposure condition, for example met at the point 1103, could beexpressed:if Pc_in=L(p) and (L(p)>K2), then Pc_out=Swghtd(Pc_in)*GS(p).

With Swghtd(Pc_in) as a substitution value, replacing the data Pc_in,for example calculated by weighted-average filtering from the read dataresulting from an acquisition with the second time of exposure B ofneighbouring pixels, advantageously as described hereinafter inconnection with FIG. 11 .

This means that when the read data Pc_in results from an acquisitionwith the first time of exposure A, and if the read data Pc_in has avalue higher than the second threshold K2, then the correspondingsubstitution data Swghtd(Pc_in) is determined from the read dataresulting from an acquisition with the second time of exposure B ofneighbouring pixels, and the second gain GS(p) is applied to thesubstitution data Swghtd(Pc_in).

The underexposure condition, for example met at the point 1104, could beexpressed:if Pc_in=S(p) and S(p)<K1/expoRatio, then Pc_out=Lwghtd(Pc_in)*GL(p).

With Lwghtd(Pc_in) as a substitution value replacing the data Pc_in, forexample calculated through a weighted-average operation from the readdata resulting from an acquisition with the first time of exposure A ofneighbouring pixels, advantageously as described hereinafter inconnection with FIG. 11 .

This means that when the read data Pc_in results from an acquisitionwith the second time of exposure B, and if the read data Pc_in has avalue lower than the first threshold K1/expoRatio, then thecorresponding substitution data Lwghtd(Pc_in) is determined from theread data resulting from an acquisition with the first time of exposureA of neighbouring pixels, and the first gain GL(p) is applied to thesubstitution data Lwghtd(Pc_in).

The exposure near-limit condition, for example met at the points 1102 or1105, could be expressed:if Pc_in=L(p) and [K1≤L(p)≤K2],then Pc_out=α*Lwghtd(Pc_in)*GL(p)+β*Swghtd(Pc_in)*GS(p)orif Pc_in=S(p) and [K1/expoRatio≤L(p)K2/expoRatio],then c_out=α*Lwghtd(Pc_in)*GL(p)+β*Swghtd(Pc_in)*GS(p).

With α and β two complementary coefficients (β=(1−α); α+β=1),respectively representative of the distance between the data Pc_in(points 1102, 1105) and the thresholds K1, K2.

This means that when the read data Pc_in has a value comprised betweenthe first threshold and the second threshold K1, K2; K1/expoRatio,K2/expoRation, then the corresponding substitution data is determinedfrom read data resulting from an acquisition with the first time ofexposure A of neighbouring pixels and also from read data resulting froman acquisition with the second time of exposure B of neighbouringpixels.

Reference is now made to FIG. 11 .

FIG. 11 illustrates an advantageous example of obtainment of thesubstitution values Lwghtd(Pc_in) and Swghtd(Pc_in) describedhereinbefore in connection with FIG. 10 .

The determination of the substitution data B_out=Lwghtd(Pc_in) orB_out=Swghtd(Pc_in) comprises a filtering calculating a weighted averagevalue of the read data resulting from an acquisition with neighbouringpixels of the pixel Pc_in in the array RES. Advantageously, the weightsare assigned to said read data according to an orientation of thespatial variations in the HDR image, in the neighbourhood NGHB of thepixel from which the read data Pc_in is derived.

The illustrated example corresponds to the case where the read data tobe replaced Pc_in is a first read data L(p), i.e. resulting from anacquisition with a first pixel and the first time of exposure A. Thepixel from which the read data Pc_in is derived is located at the middleof its neighbourhood NGHB. The neighbourhood NGHB corresponds forexample to a square of 5×5 pixels.

The neighbouring pixels belonging to the neighbourhood NGHB anddedicated to the same component, and having performed the acquisitionwith the second time of exposure B, are referred to by their cardinalpositions “north” Bn, “south” Bs, “east” Be, “west” Bw, as well as“north-east” Bne, and “south-west” Bws, with respect to the pixel to bereplaced Pc_in.

For example, the orientation of the spatial variations in the image isobtained by calculation of gradients Grad_ns, Grad_we, Grad_nw, Grad_ne,Grad_sw, Grad_se.

For example, each gradient corresponds to the oriented difference (whiletaking the sign into account) of the values of the pixels correspondingto the respective cardinal points, i.e.:Grad_ns=Bn−Bs;Grad_we=Bw−Be;Grad_nw=Bn−Bw;Grad_ne=Bn−Be;Grad_sw=Bs−Bw;Grad_se=Bs−Be;Grad_ws_ne=Bws−Bne.

The determination, done according to an orientation of the spatialvariations in the HDR image, is implemented for example by the followingalgorithm:

If Max(Grad_i) = Grad_ns, then: if Grad_ns ~= Grad_nw ~= Grad_ne, thenB_out = F(Bs;Bw;Be) else, if Grad_ns != Grad_nw and Grad_ns != Grad_ne,then B_out = F(Bn;Bw;Be). Else, if Max(Grad_i) = Grad_we, then: ifGrad_we ~= Grad_nw ~= Grad_sw, then B_out = F(Be;Bn;Bs) else, if Grad_we!= Grad_nw and Grad_we != Grad_sw, then B_out = F(Bw;Bn;Bs). Else, ifGrad_ns ~= Grad_we, then: if Grad_nw ~= Grad_se ~= Grad_ws_ne, thenB_out = F(Be;Bn;Bs;Bw; Bws;Bne) else, B_out = F(Be, Bn, Bs, Bw).

Where “Max(Grad_i)” means “the maximum value amongst the gradientsGrad_ns, Grad_we; namely i=[ns; we]”; where “˜=” means “equal or closeby less than 5%”; where “!=” means “different from”; and where thefunction “F(Bx;By;Bz)” is a weighted average function including thebarycentre to spatially distribute the weight values based on theinverse of the differences.

In this respect, in the function F(Bx;By;Bz), for example applied byF(Bw, Bn, Be), an intermediate average value “Binter” is calculatedbetween the two neighbouring pixels aligned with the processed pixelPc_in, i.e. the pixels Bw and Be in this example. Then, the weight Wi(in this example “i”=“w” or “n” or “e” respectively) is assigned to eachneighbouring pixel Bi by the following calculationWi=d/(1+abs(Bi-Binter)) with “abs( )” the “absolute value” function and“d” the distance between the processed pixel Pc_in and the neighbouringpixel Bi (d=1 laterally, and d=2^(1/2) diagonally).

To sum up, this algorithm first identifies the orientation amongst thedirections “ns” and “we” in which the image has the greatest variations,in the neighbourhood NGHB of the pixel Pc_in.

If the orientation having the greatest variation is “ns” (resp. “we”),then we check up whether the variations “nw” and “ne” (resp. “nw” and“sw”) could be compared to the variation “ns” (resp. “we”).

If so is the case, we consider that the location of Pc_in as well as thelocations of Bw and Be (resp. Bn and Bs) belong to the portion of theimage located on the “s” (resp. “e”) side of the variation, and we usethe data Bs, Bw, Be (resp. Be, Bn, Bs) for the determination of thesubstitution data B_out.

Otherwise, we consider that the location of Pc_in, as well as thelocations of Bw and Be (resp. Bn and Bs) belong to the portion of theimage located on the “n” (resp. “w”) side of the variation, and we usethe data Bn, Bw, Be (resp. Bw, Bn, Bs) for the determination of thesubstitution data B_out.

Finally, if the variations of the image in the neighbourhood NGHB of thepixel Pc_in are substantially equal in the orientations “ns” and “we”,and if, in addition, the variations in the orientations “nw”, “es” and,in particular for the green pixels, in the orientation between thediagonally-neighbouring pixels Bws and Bne are substantially equal toone another, then we consider that this region of the image NGHB has nosubstantial variation and we use all of the read data originating fromsaid neighbouring pixels for the determination. It is further possibleto use the read data of the first two pixels Anw, Ase, diagonallyneighbouring the processed pixel Pc_in, brought to their equivalentvalues in terms of second read data (by dividing them by the ratioexpoRatio=A/B).

If, on the contrary, in particular for green pixels, the variations inthe orientation between the neighbouring pixels Bws and Bne are notsubstantially equal to the variations in the other orientations, then wedo not use the pixels Bws and Bne for the determination.

Finally, although the example described in connection with FIG. 11 isgiven for a first read data Pc_in derived from a first pixel, i.e. apixel according to the first pair A-CVF1, the second read data Pc_inderived from the second pixels, i.e. the pixels according to the secondpair B-CVF2, are processed with the same algorithm wherein the usedneighbouring read data will be the first read data derived from thefirst neighbouring pixels (“An”, “Aw”, “Ae”, “As”, and possibly “Aws”,“Ane”, “Bnw”, “Bse”).

Moreover, in the digital processing of the image signals described inconnection with FIGS. 10 and 11 , the exposure limit conditions areassessed pixel-by-pixel (read data Pc_in by read data Pc_in).

That being so, the exposure limit conditions could alternatively beassessed by groups of pixels, such as the group including theneighbourhood NGHB of FIG. 11 . In other words, it is possible toconsider the average of the amplitude of the first (resp. second) readdata L(p) (resp. S(p)) to classify the point 1101-1106 of the group NGHBand calculate the possible substitution data in a corresponding mannerfor all pixels of the group NGHB.

In another alternative, the exposure limit conditions could be assessedon the maximal value of the first read data L(p) of a group NGHB offirst pixels, and respectively on the minimum value of the second readdata S(p) of a group NGHB of second pixels, to classify the point1101-1106 of the group NGHB and calculate the possible substitution datain a corresponding manner for all pixels of the group NGHB.

Examples of embodiments and of implementation of different aspects ofthe invention have been described, that being so, the invention is notlimited to these examples but encompasses all variants thereof, as wellas all combinations between the different aspects disclosed inconnection with FIGS. 1 to 11 .

Example embodiments of the invention are summarized here. Otherembodiments can also be understood from the entirety of thespecification.

Example 1. An image sensor including an array of photosensitive pixelscomprising at least two sets of at least one pixel, control circuitconfigured to generate at least two different timing signals and adaptedto control an acquisition of an incident optical signal by the pixels ofthe array, and distribution circuit configured to respectivelydistribute said at least two different timing signals in said at leasttwo sets of at least one sensor, during the same acquisition of theincident optical signal.

Example 2. The image sensor according to example 1, wherein the timingsignals are adapted to control a time of exposure of the respectivepixels to the incident optical signal.

Example 3. The image sensor according to one of examples 1 or 2, whereinthe array is arranged in rows and columns of pixels, and thedistribution circuit include a row and/or column decoder, configured toselectively access the rows and/or the columns corresponding to said atleast two sets of at least one pixel.

Example 4. The image sensor according to one of examples 1 to 3, whereinthe array comprises at least one first set of pixels configured todetect components of the visible spectrum of the incident opticalsignal, the control circuit are configured to respectively generate atleast one first timing signal, and the distribution circuit areconfigured to distribute said at least one first timing signal,respectively in said at least one first set of pixels.

Example 5. The image sensor according to example 4, wherein the arraycomprises several first sets of pixels, each corresponding to a localregion of the array.

Example 6. The image sensor according to one of examples 1 to 5, whereinthe array comprises at least one second set of pixels configured todetect an infrared component of the incident optical signal, the controlcircuit are configured to respectively generate at least one secondtiming signal, and the distribution circuit are configured to distributesaid at least one second timing signal, respectively in said at leastone second set of pixels.

Example 7. The image sensor according to one of examples 1 to 6, whereinthe array comprises at least one third set of pixels configured tomeasure information on the ambient luminosity of the incident opticalsignal, the control circuit are configured to respectively generate atleast one third timing signal, and the distribution circuit areconfigured to distribute said at least one third timing signal inrespectively said at least one third set of pixels.

Example 8. The image sensor according to example 7, wherein the thirdset of pixels includes a homogeneous spatially pseudo-randomdistribution of isolated pixels on the surface of the array.

Example 9. The image sensor according to one of examples 7 or 8, furtherincluding processing circuit dedicated to the third set of pixels andconfigured to average and filter signals photogenerated by the pixels ofthe third set during the acquisition, so as to provide information onthe overall ambient luminosity of the incident optical signal.

Example 10. The image sensor according to one of examples 7 to 9,wherein the pixels of the third set of pixels are configured to detectmultispectral components of the spectrum of the incident optical signal.

Example 11. A method for capturing an image comprising a generation ofat least two different timing signals and adapted to control anacquisition of an incident optical signal by pixels of an array ofphotosensitive pixels comprising at least two sets of at least onepixel, and a distribution of said at least two different timing signalsin said at least two sets of at least one pixel, during the sameacquisition of the incident optical signal.

Example 12. The method according to example 11, wherein the timingsignals control a time of exposure of the respective pixels of theincident optical signal.

Example 13. The method according to one of examples 11 or 12, whereinthe array is arranged in rows and columns of pixels, and thedistribution comprising a row and/or column decoding, to selectivelyaccess the rows and/or the columns corresponding to said at least twosets of at least one pixel.

Example 14. The method according to one of examples 11 to 13, comprisingan acquisition of components of the visible spectrum of the incidentoptical signal in at least one first set of pixels, controlled by atleast one first timing signal respectively distributed in said at leastone first set of pixels.

Example 15. The method according to example 14, wherein the acquisitionof the components of the visible spectrum of the incident optical signalis done in several first sets of pixels, each corresponding to a localregion of the array.

Example 16. The method according to one of examples 11 to 15, comprisingan acquisition of an infrared component of the incident optical signalin at least one second set of pixels, controlled by at least one secondtiming signal respectively distributed in said at least one second setof pixels.

Example 17. The method according to one of examples 11 to 16, comprisinga measurement of information on the ambient luminosity of the incidentoptical signal in at least one third set of pixels, controlled by atleast one third timing signal respectively distributed in said at leastone third set of pixels.

Example 18. The method according to example 17, wherein the pixels ofthe third set of pixels are distributed in a homogeneous spatiallypseudo-random manner in isolated pixels on the surface of the array.

Example 19. The method according to one of examples 17 or 18, furthercomprising a processing, comprising an averaging and a filtering of thesignals photogenerated by the pixels of the third set during theacquisition, so as to provide information on the overall ambientluminosity of the incident optical signal.

Example 20. The method according to one of examples 17 to 19, whereinthe measurement of the information on the ambient luminosity of theincident optical signal comprises an acquisition of multispectralcomponents of the spectrum of the incident optical signal.

Example 21. An image sensor including an array of photosensitive pixelsarranged in rows and columns of pixels comprising at least two sets ofpixels each corresponding to a region of the array including severaladjacent rows, control circuit configured to generate as many differenttiming signals as there are sets of pixels, the timing signals beingadapted to control a time of exposure of an acquisition of an incidentoptical signal by the pixels of the array, and distribution circuitconfigured to respectively distribute said timing signals in said setsof pixels, during the same acquisition of the incident optical signal.

Example 22. The image sensor according to example 21, wherein thedistribution circuit include a row decoder, configured to selectivelyaccess the rows of the regions of the array corresponding to said atleast two sets of pixels.

Example 23. The image sensor according to one of examples 21 or 22,wherein said regions of the array are located over a half-length of saidadjacent rows, on either side of a median of the array perpendicular tothe direction of the rows.

Example 24. The image sensor according to example 23 considered incombination with example 22, wherein the distribution circuit include afirst row decoder dedicated to a first half of the array on one side ofsaid median, as well as a second row decoder dedicated to a second halfof the array on other side of said median.

Example 25. The image sensor according to one of examples 21 or 22,wherein said regions of the array are located over the entire length inthe direction of the rows of said adjacent rows.

Example 26. The image sensor according to one of examples 21 to 24,wherein the control and distribution circuit are configured todistribute the timing signals, during said same acquisition of theincident optical signal, so that the times of exposure of the differentsets of pixels start at the same time point, or the times of exposure ofthe different sets of pixels finish at the same time point, or the timesof exposure of the different sets of pixels are distributed and includedwithin the duration of the longest time of exposure.

Example 27. The image sensor according to one of examples 21 to 26,wherein said sets of pixels comprise a first set of pixels, a third setof pixels and, between the first set and the third set, a second set ofpixels including at least two subsets of at least one row of pixels, thecontrol circuit being configured to generate first timing signalsadapted to control a first time of exposure for the first set of pixels,third timing signals adapted to control a third time of exposure, longerthan the first time of exposure, for the third set of pixels, and secondtiming signals adapted to control second times of exposure withdurations varying monotonously between the first time of exposure andthe third time of exposure, respectively from the subset of pixelsadjacent to the first set up to the subset of pixels adjacent to thethird set.

Example 28. A method for capturing an image comprising a generation ofat least two different timing signals and adapted to control a time ofexposure of an acquisition of an incident optical signal by pixels of anarray of photosensitive pixels, arranged in rows and columns of pixels,comprising as many sets of pixels as there are timing signals, each ofthe sets of pixels corresponding to a physical region of the arrayincluding several adjacent rows, the method comprising a distribution ofsaid timing signals respectively in said sets of pixels, during the sameacquisition of the incident optical signal.

Example 29. The method according to example 28, wherein the distributioncomprises a row decoding and a sequencing to selectively access the rowsof the regions of the array corresponding to said at least two sets ofpixels.

Example 30. The method according to one of examples 28 or 29, adaptedfor regions of the array located over a half-length of said adjacentrows, on either side of a median of the array perpendicular to thedirection of the rows.

Example 31. The method according to example 30 considered in combinationwith example 29, wherein the distribution comprises a first row decodingand a first sequencing dedicated to a first half of the array on oneside of said median, as well as a second row decoding and a secondsequencing dedicated to a second half of the array on the other side ofsaid median.

Example 32. The method according to one of examples 28 or 29, adaptedfor regions of the array located over the entire length in the directionof the rows of said adjacent rows.

Example 33. The method according to one of examples 28 to 32, whereinthe generation and the distribution are adapted to distribute the timingsignals, during said same acquisition of the incident optical signal, sothat the times of exposure of the different sets of pixels starting atthe same time point, or the times of exposure of the different sets ofpixels finishing at the same time point or the times of exposure of thedifferent sets of pixels are distributed and included within theduration of the longest time of exposure.

Example 34. The method according to one of examples 28 to 33, whereinthe generation of the timing signals comprises a generation of firsttiming signals adapted to control a first time of exposure for a firstset of pixels, a generation of third timing signals adapted to control athird time of exposure, longer than the first time of exposure for athird set of pixels, and a generation of second timing signals adaptedto control second times of exposure for a second set of pixels includingat least two subsets of at least one row of pixels between the first setand the third set, the second times of exposure having durations varyingmonotonously between the first time of exposure and the third time ofexposure, respectively from the subset of pixels adjacent to the firstset up to a subset of pixels adjacent to the third set.

Example 35. An image sensor according to one of examples 1 to 10 oraccording to one of examples 21 to 27, including reading circuitconfigured to provide read signals resulting from an acquisition of anincident optical signal by the pixels of the array, wherein the controlcircuit include a video timing circuit configured to assess the dynamicsof the image from a distribution of the amplitudes of the read signals,and to control a next acquisition of an incident optical signal with thetiming signals and a distribution of the timing signals in a frame modeif the dynamics is lower than first threshold, in a band mode if thedynamics is comprised between the first threshold and a secondthreshold, and in a pixel mode if the dynamics is higher than the secondthreshold.

Example 36. The image sensor according to example 35, wherein, in theframe mode, the control and distribution circuit are configured togenerate timing signals adapted to control a unique time of exposure anda distribution of these timing signals to all pixels of the array.

Example 37. The image sensor according to example 35 or 36 considered incombination with one of examples 21 to 27, wherein, in the band mode,the control and distribution circuit are configured to generate said asmany different timing signals as there are sets of pixels, and todistribute these timing signals in said sets of pixels eachcorresponding to a region of the array including several adjacent rows.

Example 38. The image sensor according to one of examples 35 to 37considered in combination with one of examples 1 to 10, wherein, in thepixel mode, the control and distribution circuit are configured togenerate said respective timing signals to each set of at least onepixel, and to distribute these timing signals in said sets of at leastone respective pixel.

Example 39. The image sensor according to one of examples 35 to 38,wherein the video timing circuit is configured, in each of said modes,to set the times of exposure controlled by the timing signals of asubsequent acquisition according to the read signals resulting from aprior acquisition, respectively in each of the different sets of pixels.

Example 40. A method for capturing an image according to one of examples11 to 20 or according to one of examples 28 to 34, comprising:

a reading providing read signals resulting from an acquisition of anincident optical signal by the pixels of the array,

an analysis of the dynamics of the image from a distribution of theamplitudes of the read signals, and

a control of a next acquisition of an incident optical signal with thetiming signals and a distribution of the timing signals in a frame modeif the dynamics is lower than a first threshold, in a band mode if thedynamics is comprised between the first threshold and a secondthreshold, and in a pixel mode if the dynamics is higher than the secondthreshold.

Example 41. The method according to example 40, wherein, in the framemode, the generation and the distribution of the timing signals areadapted to control a unique time of exposure in all pixels of the array.

Example 42. The method according to one of examples 40 or 41 consideredin combination with one of examples 28 to 34, wherein, in the band mode,the generation and the distribution of the timing signals are adapted tocontrol respective times of exposure to each of said sets of pixels eachcorresponding to a region of the array including several adjacent rows.

Example 43. The method according to one of examples 40 to 42 consideredin combination with one of examples 11 to 20, wherein, in the pixelmode, the generation and distribution of the timing signals are adaptedto control respective times of exposure to each of said sets of pixelseach corresponding to a region of the array including several adjacentrows.

Example 44. The method according to one of examples 40 to 43, wherein,in each of said modes, the times of exposure controlled by the timingsignals of a subsequent acquisition are set according to the readsignals resulting from a prior acquisition, respectively in each of thedifferent sets of pixels.

Example 45. An image sensor including an array of photosensitive pixelsdedicated to components of the spectrum of the light, each pixelincluding a photosensitive semiconductor region, a transfer gate coupledbetween the photosensitive region and a transfer node, the transfer nodehaving a capacitive value defining a charge-to-voltage conversion factorof each pixel, wherein the array of pixels is arranged according to aperiodic pattern of macro-pixels each dedicated to one component, andeach including at least one first pixel and at least one second pixeldedicated to this component, the capacitive value of the transfer nodeof the first pixel defining a first charge-to-voltage conversion factor,the capacitive value of the transfer node of the second pixel defining asecond charge-to-voltage conversion factor different from the firstcharge-to-voltage conversion factor.

Example 46. The image sensor according to example 45, wherein theperiodic pattern of macro-pixels includes at least two macro-pixelsdedicated to respective components, said first pixels and second pixelsof said at least two macro-pixels being positioned so as to becontiguous only to the first or second pixels of another macro-pixel ofthe same pattern.

Example 47. The image sensor according to example 46, wherein eachmacro-pixel includes two first pixels and two second pixels, and whereinthe periodic pattern of macro-pixels includes four macro-pixelsdedicated, respectively, to four components.

Example 48. The image sensor according to one of examples 45 to 47,including control circuit configured to generate a first timing signaland a second timing signal, different and adapted to respectivelycontrol a first time of exposure and a second time of exposure of anacquisition of an incident optical signal by the pixels of the array anddistribution circuit configured to distribute the first timing signal insaid first pixels of the macro-pixels of the array, and to distributethe second timing signal in said second pixels of the macro-pixels ofthe array, during the same acquisition of the incident optical signal.

Example 49. The image sensor according to example 48, wherein the firstcharge-to-voltage conversion factor is greater than the secondcharge-to-voltage conversion factor and the first time of exposure islonger than the second time of exposure.

Example 50. A method for capturing an image with an image sensoraccording to example 45, comprising a generation of a first timingsignal and a second timing signal, different and adapted to respectivelycontrol a first time of exposure and a second time of exposure of anacquisition of an incident optical signal by the pixels of the array,and distribution of the first timing signal in said first pixels of themacro-pixels of the array, and of the second timing signal in saidsecond pixels of the macro-pixels of the array, during the sameacquisition of the incident optical signal.

Example 51. The method according to example 50, wherein the firstcharge-to-voltage conversion factor is greater than the secondcharge-to-voltage conversion factor, and the first time of exposure islonger than the second time of exposure.

Example 52. The method according to one of examples 50 or 51, whereinthe capture method comprises:

a reading providing first read data resulting from said same acquisitionof the incident optical signal by the first pixels of the array, andsecond read data resulting from said same acquisition of the incidentoptical signal by the second pixels of the array,a reconstruction of a high dynamic range (HDR) image, comprising anapplication of a respective normalisation gain to each read data, therespective normalisation gains being adapted to compensate for thedifference between the respective times of exposure of the pixels of thearray.

Example 53. The method according to example 52, wherein thereconstruction of the HDR image further comprises, before theapplication of the normalisation gain:

an identification, for each read data, of an exposure limit conditionamongst an overexposure condition, an underexposure condition, or anear-limit condition; and

if said read data is identified in one of said exposure limitconditions, a determination of a substitution data, replacing said readdata, from the read data resulting from an acquisition with neighbouringpixels of the array dedicated to the same component.

Example 54. The method according to example 53 considered in combinationwith example 51, wherein the overexposure condition is identified if theread data results from an acquisition with the first time of exposure,and if the read data has a value greater than a second threshold, thecorresponding substitution data being determined from the read dataresulting from an acquisition with the second time of exposure of saidneighbouring pixels of the array.

Example 55. The method according to one of examples 53 or 54 consideredin combination with example 51, wherein the underexposure condition isidentified if the read data results from an acquisition with the secondtime of exposure, and if the read data has a value lower than a firstthreshold, the corresponding substitution data being determined from theread data resulting from an acquisition with the first time of exposureof said neighbouring pixels of the array.

Example 56. The method according to one of examples 53 to 55 consideredin combination with example 51, wherein the near-limit condition isidentified if the read data has a value comprised between the firstthreshold and the second threshold, the corresponding substitution databeing determined from the read data resulting from an acquisition withthe first time of exposure of said neighbouring pixels of the array andfrom the read data resulting from an acquisition with the second time ofexposure of said neighbouring pixels of the array.

Example 57. The method according to one of examples 53 to 56, whereinsaid determination of the substitution data comprises a filteringcalculating a weighted average value of said read data resulting from anacquisition with said neighbouring pixels of the array, the weightsbeing assigned to said read data according to an orientation of thespatial variations in the HDR image.

While this invention has been described with reference to illustrativeembodiments, this description is not intended to be construed in alimiting sense. Various modifications and combinations of theillustrative embodiments, as well as other embodiments of the invention,will be apparent to persons skilled in the art upon reference to thedescription. It is therefore intended that the examples encompass anysuch modifications or embodiments.

The invention claimed is:
 1. An image sensor comprising: an array ofphotosensitive pixels dedicated to components of a spectrum of thelight, each pixel including a photosensitive semiconductor region, atransfer gate coupled between the photosensitive region, and a transfernode, the transfer node having a capacitive value defining acharge-to-voltage conversion factor of each pixel, the array ofphotosensitive pixels being arranged according to a periodic pattern ofmacro-pixels each dedicated to one component, and each including a firstpixel and a second pixel dedicated to this component, the capacitivevalue of the transfer node of the first pixel defining a firstcharge-to-voltage conversion factor, the capacitive value of thetransfer node of the second pixel defining a second charge-to-voltageconversion factor different from the first charge-to-voltage conversionfactor.
 2. The image sensor according to claim 1, wherein the periodicpattern of macro-pixels includes two macro-pixels dedicated torespective components, the first pixels and second pixels of the twomacro-pixels being positioned so as to be contiguous only to the firstor the second pixels of another macro-pixel of the same pattern.
 3. Theimage sensor according to claim 2, wherein each macro-pixel includes twofirst pixels and two second pixels, and wherein the periodic pattern ofmacro-pixels includes four macro-pixels dedicated, respectively, to fourcomponents.
 4. The image sensor according to claim 1, further includinga control circuit configured to generate a first timing signal and asecond timing signal, different and adapted to respectively control afirst time of exposure and a second time of exposure of an acquisitionof an incident optical signal by the pixels of the array anddistribution circuit configured to distribute the first timing signal inthe first pixels of the macro-pixels of the array, and to distribute thesecond timing signal in the second pixels of the macro-pixels of thearray, during the same acquisition of the incident optical signal. 5.The image sensor according to claim 4, wherein the firstcharge-to-voltage conversion factor is greater than the secondcharge-to-voltage conversion factor and the first time of exposure islonger than the second time of exposure.
 6. A method for capturing animage with an image sensor comprising an array of photosensitive pixels,the method comprising: generating a first timing signal and a secondtiming signal, different and adapted to respectively control a firsttime of exposure and a second time of exposure of an acquisition of anincident optical signal by a pixels of the array of photosensitivepixels dedicated to components of a spectrum of the light, each pixelincluding a photosensitive semiconductor region, a transfer gate coupledbetween the photosensitive region, and a transfer node, the transfernode having a capacitive value defining a charge-to-voltage conversionfactor of each pixel, the array of photosensitive pixels being arrangedaccording to a periodic pattern of macro-pixels each dedicated to onecomponent, and each including a first pixel and a second pixel dedicatedto this component, the capacitive value of the transfer node of thefirst pixel defining a first charge-to-voltage conversion factor, thecapacitive value of the transfer node of the second pixel defining asecond charge-to-voltage conversion factor different from the firstcharge-to-voltage conversion factor; and distributing the first timingsignal in the first pixels of the macro-pixels of the array, and thesecond timing signal in the second pixels of the macro-pixels of thearray, during the same acquisition of the incident optical signal. 7.The method according to claim 6, wherein the periodic pattern ofmacro-pixels includes two macro-pixels dedicated to respectivecomponents, the first pixels and second pixels of the two macro-pixelsbeing positioned so as to be contiguous only to the first or the secondpixels of another macro-pixel of the same pattern.
 8. The methodaccording to claim 7, wherein each macro-pixel includes two first pixelsand two second pixels, and wherein the periodic pattern of macro-pixelsincludes four macro-pixels dedicated, respectively, to four components.9. The method according to claim 6, further comprising: generating, at acontrol circuit, a first timing signal and a second timing signal,different and adapted to respectively control a first time of exposureand a second time of exposure of an acquisition of an incident opticalsignal by the pixels of the array; and distributing, at a distributioncircuit, the first timing signal in the first pixels of the macro-pixelsof the array, and the second timing signal in the second pixels of themacro-pixels of the array, during the same acquisition of the incidentoptical signal.
 10. The method according to claim 6, wherein the firstcharge-to-voltage conversion factor is greater than the secondcharge-to-voltage conversion factor, and the first time of exposure islonger than the second time of exposure.
 11. The method according toclaim 6, further comprising: reading to provide first read data andsecond read data, the first read data resulting from the sameacquisition of the incident optical signal by the first pixels of thearray, and the second read data resulting from the same acquisition ofthe incident optical signal by the second pixels of the array; andreconstructing a high dynamic range (HDR) image, the reconstructingcomprising applying a respective normalization gain to each read data,the respective normalization gains being adapted to compensate for thedifference between the respective times of exposure of the pixels of thearray.
 12. The method according to claim 11, wherein the reconstructingfurther comprises, before the application of the normalization gain: anidentification, for each read data, of an exposure limit conditionamongst an overexposure condition, an underexposure condition, or anear-limit condition; and in response to identifying the read data inone of the exposure limit conditions, a determination of a substitutiondata, replacing the read data, from the read data resulting from anacquisition with neighboring pixels of the array dedicated to the samecomponent.
 13. The method according to claim 12, wherein thedetermination of the substitution data comprises a filtering calculatinga weighted average value of the read data resulting from an acquisitionwith the neighboring pixels of the array, the weights being assigned tothe read data according to an orientation of the spatial variations inthe HDR image.
 14. The method according to claim 6, wherein the firstcharge-to-voltage conversion factor is greater than the secondcharge-to-voltage conversion factor, and the first time of exposure islonger than the second time of exposure, wherein the capture methodcomprises: a reading providing first read data resulting from the sameacquisition of the incident optical signal by the first pixels of thearray, and second read data resulting from the same acquisition of theincident optical signal by the second pixels of the array, areconstruction of a high dynamic range (HDR) image, comprising anapplication of a respective normalization gain to each read data, therespective normalization gains being adapted to compensate for thedifference between the respective times of exposure of the pixels of thearray, wherein the reconstruction of the HDR image further comprises,before the application of the normalization gain: an identification, foreach read data, of an exposure limit condition amongst an overexposurecondition, an underexposure condition, or a near-limit condition; and inresponse to identifying the read data in one of the exposure limitconditions, a determination of a substitution data, replacing the readdata, from the read data resulting from an acquisition with neighboringpixels of the array dedicated to the same component.
 15. The methodaccording to claim 14, wherein the overexposure condition is identifiedin response to determining that the read data results from anacquisition with the first time of exposure, and if the read data has avalue greater than a second threshold, the corresponding substitutiondata being determined from the read data resulting from an acquisitionwith the second time of exposure of the neighboring pixels of the array.16. The method according to claim 14, wherein the underexposurecondition is identified in response to determining that the read dataresults from an acquisition with the second time of exposure, and if theread data has a value lower than a first threshold, the correspondingsubstitution data being determined from the read data resulting from anacquisition with the first time of exposure of the neighboring pixels ofthe array.
 17. The method according to claim 14, wherein the near-limitcondition is identified in response to determining that the read datahas a value comprised between a first threshold and a second threshold,the corresponding substitution data being determined from the read dataresulting from an acquisition with the first time of exposure of theneighboring pixels of the array and from the read data resulting from anacquisition with the second time of exposure of the neighboring pixelsof the array.
 18. The method according to claim 6, further comprising:reading to provide first read data and second read data, the first readdata resulting from the same acquisition of the incident optical signalby the first pixels of the array, and the second read data resultingfrom the same acquisition of the incident optical signal by the secondpixels of the array; and reconstructing a high dynamic range (HDR) imagefrom the first read data and the second read data.
 19. A sensing systemcomprising: a pixel array comprising a periodic pattern of firstmacro-pixels, each of the first macro-pixels configured to senseinfrared light and including a first pixel and a second pixel, each ofthe first and the second pixels comprising: a photosensitivesemiconductor region, a transfer gate coupled between the photosensitiveregion, and a transfer node, the transfer node having a capacitive valuedefining a charge-to-voltage conversion factor for each pixel, thecapacitive value of the transfer node of the first pixel defining afirst charge-to-voltage conversion factor, the capacitive value of thetransfer node of the second pixel defining a second charge-to-voltageconversion factor different from the first charge-to-voltage conversionfactor.
 20. The sensing system according to claim 19, wherein the pixelarray further comprises a periodic pattern of second macro-pixels, eachof the second macro-pixels configured to sense visible light andincluding a third pixel and a fourth pixel, each of the third and thefourth pixels comprising: a photosensitive semiconductor region, atransfer gate coupled between the photosensitive region, and a transfernode, the capacitive value of the transfer node of the third pixeldefining the first charge-to-voltage conversion factor, the capacitivevalue of the transfer node of the fourth pixel defining the secondcharge-to-voltage conversion factor.
 21. The sensing system according toclaim 19, wherein the sensing system is configured to produce a highdynamic range image by combining the information from the first pixeland the second pixel.